2009年12月大学英语四级考试模拟试题(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]对话一开始就谈论人类骨骼的问题，女士说 But the fact is bones are made of dynamic living tissue that requires continuous maintenance and repair. 后面的对话都是针对这个话题展开的讨论，可见整个对话讨论的话题是骨头的自我修复能力。

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

　　【解析】[C]男士解释了第一组细胞的作用，第一组细胞生成一种化学物质分解骨组织(This group of cells produces the chemical that actually breaks down the bone tissue…)，由此可见答案是They break down bone tissue.

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

　　【解析】[B]女士说这种特殊细胞作用于人类骨头的过程相当复杂，事实上，连研究人类骨头的科学家都不能完全了解这个过程。从这一句中可以知道：In fact, the scientists who study human bones don't completely understand it yet. 所以答案即是这些科学家也不知道这些细胞如何工作。

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

　　【解析】[A]学习这些人类骨头中的特殊细胞的重要目的是为了学习如何预防骨头疾病。从男士的这一句话中可看出：That'll prevent the disease from ever occurring. 这样可以在疾病发生之前预防疾病，可见[A]符合题意。

　　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.