Unit 2 The animal world单元知识总结及重点易错（专项训练）-2026-2027学年北师大版（三起）英语四年级上册

**基本信息** 聚焦动物主题核心语法，以10个易错考点为纲，通过基础-提升-拓展三级训练体系，系统提炼规则并结合情境应用，强化语言能力与思维品质。 **专项设计** |模块|题量/典例|方法提炼|知识逻辑| |----|-----------|----------|----------| |10个语法考点|每考点9题（3基础+3提升+3拓展）|提炼like+doing、三单变化等10类规则，解析错误类型|从单一语法点（如like用法）到综合描述（肯定/否定/疑问），层层递进|

最新北师大版（三起）四年级上册 Unit 2 The animal world 单元知识总结及重点易错专项训练 ■ ■ ■ ■ ■ ■ ■ 说明：本练习紧扣最新教材精选 10 个重点易错考点，每个考点含基础题×3、提升题×3、拓展题×3，共 90 题。 ★ 重点单词 █ 重点单词（动物名称 / 形容词 / 动词） animal 动物, elephant 大象, monkey 猴子, panda 熊猫, tiger 老虎, lion 狮子, bear 熊, giraffe 长颈鹿, zebra 斑马, snake 蛇, rabbit 兔子, duck 鸭子 farm 农场, wild 野生的, zoo 动物园, feed 喂养, keep 饲养, grass 草, meat 肉, leaf 叶子, fast 快的, slow 慢的, cute 可爱的, strong 强壮的, dangerous 危险的 ★ 重点短语 █ 重点短语 in the zoo 在动物园, on the farm 在农场, wild animals 野生动物, farm animals 农场动物 feed the animals 喂动物, keep a pet 养宠物, eat grass/meat/leaves 吃草/肉/叶子 run fast 跑得快, walk slowly 走得慢, look at 看…, take care of 照顾, be dangerous 危险 ★ 重点句型 █ 重点句型 — What animals do you like? — I like pandas. — Do you like tigers? — Yes, I do. / No, I don't. — Does she like monkeys? — Yes, she does. / No, she doesn't. It eats grass. / They don't eat meat. / Can it swim? — Yes, it can. Let's go to the zoo. / Don't feed the animals. ★ 重点语法 █ 重点语法 ① like + 动名词 doing（like eating / like running） ② 一般现在时三单：like→likes, eat→eats, run→runs ③ Do/Does 一般疑问句及 Yes/No 回答 ④ 否定句：don't / doesn't + 动词原形 ⑤ 情态动词 can + 动词原形（表能力） ⑥ 名词复数特殊变化：monkey→monkeys, baby→babies, leaf→leaves ⑦ 祈使句：Feed... / Don't feed... / Let's... / Look at... ⑧ 形容词：fast / slow / cute / strong / dangerous ⑨ What animals do/does ... like? 特殊疑问句 ⑩ 综合：动物描述全流程（肯定/否定/疑问/回答） 考点1：考点一：like + 动名词 doing（不是动词原形，也不是 to do） 基础题：（选择题） ◇（ ）1. I like ____ football after school. A. play B. playing C. to play ◇（ ）2. Olivia likes ____ ping-pong with her friends. A. play B. plays C. playing ◇（ ）3. They like ____ in the pool. A. swim B. swimming C. to swim 提升题：（选择题） ▷（ ）1. Jam enjoys sport. He likes ____ basketball every day. A. play B. to play C. playing ▷（ ）2. Which is WRONG? A. I like running. B. She likes dance. C. They like jumping. ▷（ ）3. Chen Wei ____ like swimming; he likes football. A. doesn't B. don't C. isn't 拓展题：（选择题） ★（ ）1. The rule: after "like / enjoy / love", we use verb + ____. A. -ing B. to do C. -ed ★（ ）2. Identify the correct structure: like + ____ + object. A. verb-ing B. verb base C. infinitive ★（ ）3. In ____ (Qingdao), kids like ____ on the beach. A. run B. running C. to run 考点2：考点二：一般现在时第三人称单数（he/she/it）动词变化 基础题：（选择题） ◇（ ）1. Lily ____ pandas very much. A. like B. likes C. liking ◇（ ）2. The monkey ____ bananas every day. A. eat B. eats C. eating ◇（ ）3. Zhou Kai ____ fast. He is good at running. A. run B. runs C. running 提升题：（选择题） ▷（ ）1. Olivia ____ like tigers because they are dangerous. A. don't B. doesn't C. isn't ▷（ ）2. Which verb change is RIGHT? A. monkey→monkeies B. eat→eats C. run→runes ▷（ ）3. The panda ____ bamboo. It ____ cute. A. eat; is B. eats; is C. eats; are 拓展题：（选择题） ★（ ）1. Rule: for verbs ending in -ch/-sh/-s/-x, add ____ in third person. A. -s B. -es C. -ies ★（ ）2. Transform: "I eat meat." → "He ____ meat." A. eat B. eats C. eating ★（ ）3. In ____ (Kunming), the zoo keeper ____ the animals every morning. A. feed B. feeds C. feeding 考点3：考点三：Do / Does 一般疑问句及 Yes / No 回答 基础题：（选择题） ◇（ ）1. — ____ you like rabbits? — Yes, I do. A. Do B. Does C. Are ◇（ ）2. — ____ she like giraffes? — No, she doesn't. A. Do B. Does C. Is ◇（ ）3. — Do they like ducks? — ____, they don't. A. Yes B. No C. Not 提升题：（选择题） ▷（ ）1. — Does Zhang Hao like snakes? — ____, he doesn't. A. Yes B. No C. Not ▷（ ）2. Which answer is RIGHT? — Do you like lions? — ____ A. Yes, I like. B. Yes, I am. C. Yes, I do. ▷（ ）3. — ____ Bella and Lily like monkeys? — Yes, they do. A. Do B. Does C. Are 拓展题：（选择题） ★（ ）1. Rule: use "____" with I/you/we/they; use "____" with he/she/it. A. do; does B. does; do C. do; do ★（ ）2. In ____ (Wuhan), people ask "____ you like pandas?" A. Do B. Does C. Are ★（ ）3. Identify the correct short answer: — Does she like it? — ____ A. Yes, she like. B. Yes, she does. C. Yes, she do. 考点4：考点四：否定句 don't / doesn't + 动词原形 基础题：（选择题） ◇（ ）1. I ____ like snakes. They are scary. A. don't B. doesn't C. not ◇（ ）2. She ____ eat meat. She is a vegetarian. A. don't B. doesn't C. isn't ◇（ ）3. We ____ keep a pet at home. A. don't B. doesn't C. not 提升题：（选择题） ▷（ ）1. Jam ____ like the zoo because it is too noisy. A. don't B. doesn't C. isn't ▷（ ）2. Which is WRONG? A. I don't like lions. B. She doesn't likes tigers. C. They don't eat meat. ▷（ ）3. Chen Wei ____ run fast, but he ____ jump high. A. don't; doesn't B. doesn't; doesn't C. don't; don't 拓展题：（选择题） ★（ ）1. Rule: after "don't / doesn't", the verb must be in ____. A. -s form B. original form C. -ing form ★（ ）2. Correct the error: "He doesn't likes rabbits." → "He ____ like rabbits." A. don't B. doesn't C. isn't ★（ ）3. In ____ (Xiamen), people ____ often keep wild animals as pets. A. don't B. doesn't C. isn't 考点5：考点五：情态动词 can + 动词原形（表能力） 基础题：（选择题） ◇（ ）1. Birds ____ fly in the sky. A. can B. cans C. can to ◇（ ）2. A fish ____ swim, but it ____ walk. A. can; can't B. can't; can C. cans; can't ◇（ ）3. — Can Olivia run fast? — Yes, she ____. A. can B. can't C. does 提升题：（选择题） ▷（ ）1. The monkey ____ climb trees very well. A. can B. cans C. can to ▷（ ）2. Which is WRONG? A. I can swim. B. She can runs fast. C. They can jump. ▷（ ）3. Lily ____ ride a horse, so she is a little afraid. A. can B. can't C. cans 拓展题：（选择题） ★（ ）1. Rule: after "can / can't", the verb must be in ____. A. -s form B. original form C. -ing form ★（ ）2. In ____ (Jinan), kids ____ often see wild rabbits in the park. A. can B. cans C. can to ★（ ）3. Identify the correct negative: "The snake ____ dance." A. can B. can't C. cans 考点6：考点六：名词复数特殊变化（monkey→monkeys, baby→babies, leaf→leaves） 基础题：（选择题） ◇（ ）1. I see two ____ in the zoo. A. monkey B. monkeys C. monkeies ◇（ ）2. There are many ____ on the tree. A. leaf B. leafs C. leaves ◇（ ）3. The cat has three ____. A. babys B. babies C. baby 提升题：（选择题） ▷（ ）1. Which plural is WRONG? A. tigers B. snakes C. bearies ▷（ ）2. There are many ____ in the farm. A. duck B. ducks C. duckes ▷（ ）3. We see some ____ eating grass. A. zebra B. zebras C. zebraes 拓展题：（选择题） ★（ ）1. Rule: for nouns ending in consonant + y, change y to i and add ____. A. -s B. -es C. -ies ★（ ）2. Transform: "one leaf" → "three ____". A. leafs B. leaves C. leafes ★（ ）3. In ____ (Qingdao), we see many sea ____ on the beach. A. baby B. babys C. babies 考点7：考点七：祈使句（Feed... / Don't feed... / Let's... / Look at...） 基础题：（选择题） ◇（ ）1. ____ the animals. They are hungry. A. Feed B. Feeds C. Feeding ◇（ ）2. ____ run in the classroom. A. Not B. Don't C. Doesn't ◇（ ）3. ____ look at the cute panda over there! A. Let's B. Don't C. Let 提升题：（选择题） ▷（ ）1. Which is a correct imperative? A. Doesn't feed the lions. B. Don't feed the lions. C. Not feed the lions. ▷（ ）2. ____ quiet in the library. The baby is sleeping. A. Be B. Is C. Are ▷（ ）3. ____ us go to the zoo this weekend! A. Let B. Let's C. Don't 拓展题：（选择题） ★（ ）1. Rule: an imperative sentence starts with a ____ (not third-person -s). A. noun B. verb base form C. verb -s ★（ ）2. In ____ (Kunming), the zoo says: "____ touch the animals." A. Please B. Don't C. Let's ★（ ）3. Identify the structure: "Look at the monkey." = ____ + prep + object. A. verb base B. verb -s C. verb -ing 考点8：考点八：形容词 fast / slow / cute / strong / dangerous 的用法 基础题：（选择题） ◇（ ）1. The rabbit runs very ____. A. fast B. faster C. fastly ◇（ ）2. The turtle walks ____. A. slow B. slowly C. slowest ◇（ ）3. Pandas are very ____. A. cute B. cutely C. cuter 提升题：（选择题） ▷（ ）1. The lion is ____. Don't go near it. A. dangerous B. dangerously C. more dangerous ▷（ ）2. Elephants are big and ____. A. strong B. strongly C. stronger ▷（ ）3. Which is WRONG? A. The snake is dangerous. B. It runs fast. C. He is strong boy. 拓展题：（选择题） ★（ ）1. Rule: after the verb "be" (is/am/are), we use an ____, not an adverb. A. adjective B. adverb C. noun ★（ ）2. In ____ (Wuhan), people describe the zoo as "____ but fun". A. dangerous B. dangerously C. danger ★（ ）3. Identify: "The monkey is cute." → "cute" is a/an ____. A. adverb B. adjective C. verb 考点9：考点九：What animals do / does ... like? 特殊疑问句 基础题：（选择题） ◇（ ）1. — What animals ____ you like? — I like rabbits. A. do B. does C. are ◇（ ）2. — What animals ____ she like? — She likes cats. A. do B. does C. is ◇（ ）3. — What animals do they like? — ____ like dogs. A. He B. She C. They 提升题：（选择题） ▷（ ）1. — What animals ____ Zhang Hao like? — He likes monkeys. A. do B. does C. are ▷（ ）2. Which question is WRONG? A. What animals do you like? B. What animals does she likes? C. What animals do they like? ▷（ ）3. — What animals does Lily like? — ____ likes pandas. A. He B. She C. They 拓展题：（选择题） ★（ ）1. Rule: "What animals" is followed by ____ + subject + verb. A. do/does B. is/are C. am/is ★（ ）2. In ____ (Xiamen), we ask "What animals ____ you like?" A. do B. does C. are ★（ ）3. Identify the correct pattern: What animals + ____ + she + ____? A. do; like B. does; likes C. does; like 考点10：考点十：综合辨析——动物描述全流程（肯定/否定/疑问/回答） 基础题：（选择题） ◇（ ）1. — Does the tiger eat meat? — Yes, ____ does. A. he B. she C. it ◇（ ）2. Olivia ____ like snakes because they are scary. A. don't B. doesn't C. isn't ◇（ ）3. The giraffe ____ (eat) leaves. It ____ (be) tall. A. eats; is B. eat; are C. eats; are 提升题：（选择题） ▷（ ）1. Which sentence is RIGHT? A. She don't like lions. B. He doesn't likes monkeys. C. They don't eat meat. ▷（ ）2. Choose the correct one: "____ you like pandas?" "Yes, I ____." A. Do; do B. Does; does C. Do; am ▷（ ）3. The zebra ____ run fast, and it ____ black and white. A. can; is B. can't; are C. cans; is 拓展题：（选择题） ★（ ）1. In ____ (Jinan), a student writes: "I ____ like spiders, but my sister ____." A. don't; does B. doesn't; do C. don't; do ★（ ）2. The complete correct description: "Pandas ____ (like) bamboo, they ____ (be) cute." A. likes; is B. like; are C. like; is ★（ ）3. Best summary of Unit 2 grammar: animals + ____ + verb forms. A. one B. two C. three 参考答案与详细解析 考点1：考点一：like + 动名词 doing（不是动词原形，也不是 to do） 基础题答案与解析： 1. I like ____ football after school. 答案：B 解析：like 后接动名词 doing，play→playing。 2. Olivia likes ____ ping-pong with her friends. 答案：C 解析：like 后接 doing，play→playing。 3. They like ____ in the pool. 答案：B 解析：like 后接 doing，swim→swimming（双写 m 加 ing）。 提升题答案与解析： 1. Jam enjoys sport. He likes ____ basketball every day. 答案：C 解析：like 后接 doing，play→playing。 2. Which is WRONG? 答案：B 解析：She 是三单，应为 likes dancing，不是 likes dance。 3. Chen Wei ____ like swimming; he likes football. 答案：A 解析：Chen Wei 是三单，否定用 doesn't。 拓展题答案与解析： 1. The rule: after "like/enjoy/love", we use verb + ____. 答案：A 解析：这三个词后都接 -ing 形式。 2. Identify the correct structure: like + ____ + object. 答案：A 解析：正确结构为 like + verb-ing + 宾语。 3. In Qingdao, kids like ____ on the beach. 答案：B 解析：like 后接 doing，run→running。 考点2：考点二：一般现在时第三人称单数（he/she/it）动词变化 基础题答案与解析： 1. Lily ____ pandas very much. 答案：B 解析：Lily 是三单，like→likes。 2. The monkey ____ bananas every day. 答案：B 解析：monkey 三单，eat→eats。 3. Zhou Kai ____ fast. He is good at running. 答案：B 解析：Zhou Kai 三单，run→runs。 提升题答案与解析： 1. Olivia ____ like tigers because they are dangerous. 答案：B 解析：Olivia 三单，否定用 doesn't。 2. Which verb change is RIGHT? 答案：B 解析：eat 三单加 s 变 eats；monkey 应变 monkeys；run 应变 runs。 3. The panda ____ bamboo. It ____ cute. 答案：B 解析：panda 三单 eats；it 对应 be 动词 is。 拓展题答案与解析： 1. Rule: for verbs ending in -ch/-sh/-s/-x, add ____ in third person. 答案：B 解析：这些结尾加 -es，如 watch→watches。 2. Transform: "I eat meat." → "He ____ meat." 答案：B 解析：三单 eats。 3. In Kunming, the zoo keeper ____ the animals every morning. 答案：B 解析：keeper 三单，feed→feeds。 考点3：考点三：Do / Does 一般疑问句及 Yes / No 回答 基础题答案与解析： 1. — ____ you like rabbits? — Yes, I do. 答案：A 解析：you 搭配 Do。 2. — ____ she like giraffes? — No, she doesn't. 答案：B 解析：she 是三单，用 Does。 3. — Do they like ducks? — ____, they don't. 答案：B 解析：don't 对应 No。 提升题答案与解析： 1. — Does Zhang Hao like snakes? — ____, he doesn't. 答案：B 解析：doesn't 对应 No。 2. Which answer is RIGHT? 答案：C 解析：Do 问用 do 答：Yes, I do. 是正确简答。 3. — ____ Bella and Lily like monkeys? — Yes, they do. 答案：A 解析：Bella and Lily 是复数，用 Do。 拓展题答案与解析： 1. Rule: use "do" with I/you/we/they; use "does" with he/she/it. 答案：A 解析：人称与助动词搭配规则。 2. In Wuhan, people ask "____ you like pandas?" 答案：A 解析：you 搭配 Do。 3. Identify the correct short answer: — Does she like it? — ____ 答案：B 解析：Does 问用 does 答：Yes, she does. 考点4：考点四：否定句 don't / doesn't + 动词原形 基础题答案与解析： 1. I ____ like snakes. They are scary. 答案：A 解析：I 搭配 don't + 动原。 2. She ____ eat meat. She is a vegetarian. 答案：B 解析：she 三单，否定用 doesn't + 动原 eat。 3. We ____ keep a pet at home. 答案：A 解析：we 复数，用 don't + 动原。 提升题答案与解析： 1. Jam ____ like the zoo because it is too noisy. 答案：B 解析：Jam 三单，否定用 doesn't。 2. Which is WRONG? 答案：B 解析：doesn't 后接动词原形 like，不是 likes。 3. Chen Wei ____ run fast, but he ____ jump high. 答案：B 解析：Chen Wei 三单，两空都用 doesn't。 拓展题答案与解析： 1. Rule: after "don't/doesn't", the verb must be in ____. 答案：B 解析：否定助动词后接动词原形。 2. Correct the error: "He doesn't likes rabbits." → "He ____ like rabbits." 答案：B 解析：doesn't 后接动词原形 like。 3. In Xiamen, people ____ often keep wild animals as pets. 答案：A 解析：people 复数，用 don't。 考点5：考点五：情态动词 can + 动词原形（表能力） 基础题答案与解析： 1. Birds ____ fly in the sky. 答案：A 解析：can 后接动词原形 fly。 2. A fish ____ swim, but it ____ walk. 答案：A 解析：鱼能游泳用 can；不能走路用 can't。 3. — Can Olivia run fast? — Yes, she ____. 答案：A 解析：Can 问用 can 答。 提升题答案与解析： 1. The monkey ____ climb trees very well. 答案：A 解析：can 后接动词原形 climb。 2. Which is WRONG? 答案：B 解析：can 后接动词原形 run，不是 runs。 3. Lily ____ ride a horse, so she is a little afraid. 答案：B 解析：不能骑马用 can't。 拓展题答案与解析： 1. Rule: after "can/can't", the verb must be in ____. 答案：B 解析：情态动词后接动词原形。 2. In Jinan, kids ____ often see wild rabbits in the park. 答案：A 解析：能看见用 can + 原形 see。 3. Identify the correct negative: "The snake ____ dance." 答案：B 解析：蛇不能跳舞用 can't。 考点6：考点六：名词复数特殊变化（monkey→monkeys, baby→babies, leaf→leaves） 基础题答案与解析： 1. I see two ____ in the zoo. 答案：B 解析：monkey 复数直接加 s → monkeys。 2. There are many ____ on the tree. 答案：C 解析：leaf 复数特殊变化：f→v 加 es → leaves。 3. The cat has three ____. 答案：B 解析：baby 辅音+y 结尾，变 y 为 i 加 es → babies。 提升题答案与解析： 1. Which plural is WRONG? 答案：C 解析：bear 复数直接加 s → bears，不是 bearies。 2. There are many ____ in the farm. 答案：B 解析：duck 复数直接加 s → ducks。 3. We see some ____ eating grass. 答案：B 解析：zebra 复数直接加 s → zebras。 拓展题答案与解析： 1. Rule: for nouns ending in consonant+y, change y to i and add ____. 答案：C 解析：辅音+y 变 ies，如 baby→babies。 2. Transform: "one leaf" → "three ____". 答案：B 解析：leaf 复数 leaves。 3. In Qingdao, we see many sea ____ on the beach. 答案：C 解析：baby 复数 babies。 考点7：考点七：祈使句（Feed... / Don't feed... / Let's... / Look at...） 基础题答案与解析： 1. ____ the animals. They are hungry. 答案：A 解析：祈使句以动词原形开头，Feed 喂养。 2. ____ run in the classroom. 答案：B 解析：否定祈使句：Don't + 动词原形。 3. ____ look at the cute panda over there! 答案：A 解析：Let's + 动词原形，让我们… 提升题答案与解析： 1. Which is a correct imperative? 答案：B 解析：Don't feed the lions. 正确否定祈使句。 2. ____ quiet in the library. The baby is sleeping. 答案：A 解析：Be + 形容词，祈使句。 3. ____ us go to the zoo this weekend! 答案：B 解析：Let's = Let us，后接动词原形 go。 拓展题答案与解析： 1. Rule: an imperative sentence starts with a ____. 答案：B 解析：祈使句以动词原形开头。 2. In Kunming, the zoo says: "____ touch the animals." 答案：B 解析：禁止触摸用 Don't touch。 3. Identify the structure: "Look at the monkey." 答案：A 解析：Look 是动词原形，at 是介词。 考点8：考点八：形容词 fast / slow / cute / strong / dangerous 的用法 基础题答案与解析： 1. The rabbit runs very ____. 答案：A 解析：fast 既是形容词也是副词，修饰 run 用 fast。 2. The turtle walks ____. 答案：B 解析：修饰动词 walk 用副词 slowly。 3. Pandas are very ____. 答案：A 解析：are 后接形容词 cute。 提升题答案与解析： 1. The lion is ____. Don't go near it. 答案：A 解析：is 后接形容词 dangerous。 2. Elephants are big and ____. 答案：A 解析：are 后接形容词 strong。 3. Which is WRONG? 答案：C 解析：He is a strong boy. 应为形容词 strong，不是副词 strongly。 拓展题答案与解析： 1. Rule: after the verb "be", we use an ____, not an adverb. 答案：A 解析：be 动词后接形容词。 2. In Wuhan, people describe the zoo as "____ but fun". 答案：A 解析：is 后接形容词 dangerous。 3. Identify: "The monkey is cute." → "cute" is a/an ____. 答案：B 解析：cute 是形容词，描述猴子特征。 考点9：考点九：What animals do / does ... like? 特殊疑问句 基础题答案与解析： 1. — What animals ____ you like? — I like rabbits. 答案：A 解析：you 搭配 do。 2. — What animals ____ she like? — She likes cats. 答案：B 解析：she 三单搭配 does。 3. — What animals do they like? — ____ like dogs. 答案：C 解析：they 对应 They like。 提升题答案与解析： 1. — What animals ____ Zhang Hao like? — He likes monkeys. 答案：B 解析：Zhang Hao 三单，用 does。 2. Which question is WRONG? 答案：B 解析：does 后接动词原形 like，不是 likes。 3. — What animals does Lily like? — ____ likes pandas. 答案：B 解析：Lily 对应 She。 拓展题答案与解析： 1. Rule: "What animals" is followed by ____ + subject + verb. 答案：A 解析：疑问词后接 do/does。 2. In Xiamen, we ask "What animals ____ you like?" 答案：A 解析：you 搭配 do。 3. Identify: What animals + ____ + she + ____? 答案：C 解析：三单用 does；后面的动词用原形 like。 考点10：考点十：综合辨析——动物描述全流程（肯定/否定/疑问/回答） 基础题答案与解析： 1. — Does the tiger eat meat? — Yes, ____ does. 答案：C 解析：the tiger 用 it 指代。 2. Olivia ____ like snakes because they are scary. 答案：B 解析：Olivia 三单，否定用 doesn't。 3. The giraffe ____ (eat) leaves. It ____ (be) tall. 答案：A 解析：giraffe 三单 eats；it 对应 is。 提升题答案与解析： 1. Which sentence is RIGHT? 答案：C 解析：they 复数，否定用 don't；eat 用原形。 2. Choose the correct one. 答案：A 解析：you 搭配 Do；回答用 do。 3. The zebra ____ run fast, and it ____ black and white. 答案：A 解析：斑马能跑用 can；it 对应 is。 拓展题答案与解析： 1. In Jinan, a student writes. 答案：A 解析：I 用 don't；my sister 三单用 does。 2. The complete correct description. 答案：B 解析：Pandas 复数用 like；they 对应 are。 3. Best summary of Unit 2 grammar. 答案：C 解析：本单元涉及三种动词形式：原形、三单-s、动名词-ing。 学科网（北京）股份有限公司 $