2009年12月大學英語四級考試模擬試題(十)

　　W: Ok. So can you tell us how the bones repair themselves?

　　M: Sure. See, there are two groups of different types of specialized cells in the bone that work together to do it. The first group goes to an area of the bone that needs repair. This group of cells produces the chemical that actually breaks down the bone tissue, and leaves a hole in it. After that the second group of specialized cells comes and produces the new tissue that fills in the hole that was made by the first group.

　　W: Very good. This is a very complex process. In fact, the scientists who study human bones don't completely understand it yet. They are still trying to find out how it all actually works. Specifically, because sometimes after the first group of cells leaves a hole in the bone tissue, for some reason, the second group doesn't completely fill in the hole. And this can cause real problems. It can actually lead to a disease in which the bone becomes weak and is easily broken.

　　M: Ok, I get it. So if the scientists can figure out what makes the specialized cells work, maybe they can find a way to make sure the second group of cells completely fills the hole in the bone tissue every time. That'll prevent the disease from ever occurring.

　　Questions 19 to 22 are based on the conversation you have just heard.

　　19. What is the discussion mainly about?

　　【解析】[C]對話一開始就談論人類骨骼的問題，女士說 But the fact is bones are made of dynamic living tissue that requires continuous maintenance and repair. 后面的對話都是針對這個話題展開的討論，可見整個對話討論的話題是骨頭的自我修復能力。

　　20. What is the function of the first group of specialized cells discussed in the talk?

　　【解析】[C]男士解釋了第一組細胞的作用，第一組細胞生成一種化學物質分解骨組織(This group of cells produces the chemical that actually breaks down the bone tissue…)，由此可見答案是They break down bone tissue.

　　21. What does the professor say about scientists who study the specialized cells in human bones?

　　【解析】[B]女士說這種特殊細胞作用于人類骨頭的過程相當復雜，事實上，連研究人類骨頭的科學家都不能完全了解這個過程。從這一句中可以知道：In fact, the scientists who study human bones don't completely understand it yet. 所以答案即是這些科學家也不知道這些細胞如何工作。

　　22. According to the student, what is one important purpose of studying specialized cells in human bones?

　　【解析】[A]學習這些人類骨頭中的特殊細胞的重要目的是為了學習如何預防骨頭疾病。從男士的這一句話中可看出：That'll prevent the disease from ever occurring. 這樣可以在疾病發(fā)生之前預防疾病，可見[A]符合題意。

　　Conversation Two

　　M: Hi Diana, mind if I sit down?

　　W: Not at all, Jerry. How have you been?

　　M: Good. But I'm surprised to see you on the city bus. Your car in the shop?

　　W: No. I've just been thinking a lot about the environment lately. So I decided the air will be a lot cleaner if we all use public transportation when we could.