专题17 阅读理解E篇 -冲刺2022-2023学年八年级下册英语期末考试满分必刷题

冲刺2022-2023年八年级下册英语期末考试满分必刷题 阅读理解E篇 Most viruses(病毒) can be found and killed by our immune system(免疫系统) as soon as they enter our bodies. However, some viruses, for example, the coronavirus, are different. They are difficult to be found. These viruses can cause deadly diseases, like COVID-19. Human-to-human transmission can easily happen, and pandemic(大流行) will therefore break out. Vaccination(接种疫苗) is by now a simple, safe and effective(有效的) way to protect us from the diseases. _____*____Vaccines are something that “looks” exactly the same as the viruses, mainly made from the viruses that are weakened or killed. They will not make us really ill. They only excite and activate our immune system to work, telling it something bad is coming in. The immune system will know what the “viruses” look like and send B cells(lymphocytes) or antibodies to find and kill them. Meanwhile B cells will remember them for the next kill. Scientists have developed more than 180 vaccines(疫苗) to fight against COVID-19. The technical ways of these vaccines can be a little different, but their aims are the same. Take the inactivated vaccine as an example. In an inactivated vaccine, the coronaviruses are already killed or changed into the ones that are unable to make more new viruses. When the immune system “sees” them, it will try to kill them. We need to take the vaccine more than one time so that B cells can remember them. Though this vaccine is safe, it might not be as effective as it is expected to be. The live-attenuated vaccine is different. In this vaccine, the viruses are weakened, but they are alive. They can make enough new viruses to train the immune system to kill and remember them, so people only need to take the vaccine once. The live-attenuated vaccine is considered the most effective, but there is worry: what might happen once these viruses wake up? In short, although vaccination is by now one of the best ways to protect us from COVID-19, it can be better. 1．The coronav