黑龙江省鹤岗市第一中学2020-2021学年高二下学期期末考试英语试题

鹤岗一中2020—2021学年度高二下学期期末考试试题 英 语 时间： 100分钟 满分：120分 第一部分 阅读理解（共两节，满分40分） 第一节（共15小题：每小题2分，满分30分） 阅读下列短文，从每题所给的四个选项（A、B、C和D）中，选出最佳选项，并在答题卡上将该项涂黑。 A Unsolved Mysteries about the Planet Earth Mystery 1: Where did water come from? Water covers more than 70 percent of the Earth’s surface and that makes the Earth earn the nickname “the blue planet”. Then where did water come from? The most popular scientific theory states that the H2O came from several violent asteroids(小行星) covered with ice. Another suggests that the water actually has been around since the Earth’s formation. However it happened, though, it’s certainly worked out well for the Earth life forms. Mystery 2: What about all the oxygen? Another thing is the planet’s oxygen. Tiny creatures released oxygen as a waste product, filling the atmosphere with it. After that, the level of oxygen in the Earth’s atmosphere went wildly up and down until it finally calmed down around 540 million years ago. Since then, it’s remained at about the breathable level we know today. But what caused it to be suddenly steady? Mystery 3: What caused the Cambrian(寒武纪）Explosion? The Cambrian Explosion refers to the explosion of complex life forms that occurred on Earth about 540 million years ago. Before then, life had consisted mostly of microbes. But at the beginning of the Cambrian period complex creatures began developing at a rate never seen before. Suddenly, life forms had brains, eyes, and bones. Most living creatures today can trace their blood back to the Cambrian period. Mystery 4: Will we be able to predict earthquakes? We still haven’t been able to come up with a way to accurately predict earthquakes. We can certainly try, but our current technology cannot predict them exactly. We know that earthquakes start when the rock cracks underground and the enormous energy released in the process causes vibration, which generates earthquake waves, but we haven’t figured out why that happens, or how to predict it. 1. What w