听力材料：

　　W: Good morning, class. Today I thought we wouldtalk about something bright and cheerful-the sun.Can anyone tell me how you feel

　　when it's sunny compared to how you feel when it'scloudy?

　　M: I find that it's a lot easier to get up in themorning if it's sunny.

　　W: Well, what if I told you that it would rain for weeks on end with no break.

　　M: I don't think I would like that very much.

　　W: Most of the articles we read lately regarding the sun are discussing the negative effects ofstaying in the sun for too long, saying that ultraviolet radiation from the sun is a major causeof skin cancer. [19]Although these articles are factual, the sun does have some positive sideeffects as well. As a matter of fact some scientists believe sunlight may reduce the risk ofseveral types of cancer.

　　M: Excuse me, but many articles that I've read state that it can take as little as 30 minutes toget a sunburn.

　　W: True, but in small doses, the sun can be quite healthy for you. In fact, recent studies havefound that [19]/[20]sunlight can actually help protect you from certain types of cancer suchas breast and stomach. More importantly, [21]the sun also provides us with our main sourceof Vitamin D.

　　M: Well, I don't need to worry about vitamins because I take multi-vitamins every day.

　　W: That's great, but wouldn't it be better if you didn't have to take them and you were able toget vitamins in a more natural way such as food and the sun?

　　M: Does that mean we should spend all day in the sun without any protection?

　　W: No, [21]spending roughly ten minutes per day in the sun should be enough to supply uswith all the Vitamin D that we need.

　　Questions 19 to 21 are based on the conversation you have just heard.

　　19. What does the teacher mainly want to tell her students in this class?

　　正确答案：D

　　解析：老师在承认长时间晒太阳的害处后强调的是其益处，答案为D。说法过于的选项不能选，可直接排除B。另外有悖常识的选项一般也不能选，可排除C。

　　20. What kind of cancer may the sunlight protects us from?

　　正确答案：A

　　解析：A是老师提到阳光可以防御癌症后列举的例子之一。B是曝晒导致的。

　　21. What is the main function of sunshine when concerned with our bodies?

　　正确答案：B

　　解析：B为两次提及的明示信息，特别是最后重申时应该重视。A只是男士的一种感受。Vitamin D属于对话后半段的高频词汇，往往就是答案。

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