Now you'll hear the two long conversations.
Conversation One
W: Good morning, class. Today I thought we would talk 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's cloudy?
M: I find that it's a lot easier to get up in the morning 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 of staying in the sun for too long, saying that ultraviolet radiation from the sun is a major cause of skin cancer. [19]Although these articles are factual, the sun does have some positive side effects as well. As a matter of fact some scientists believe sunlight may reduce the risk of several types of cancer.
M: Excuse me, but many articles that I've read state that it can take as little as 30 minutes to get a sunburn.
W: True, but in small doses, the sun can be quite healthy for you. In fact, recent studies have found that [19]/[20]sunlight can actually help protect you from certain types of cancer such as breast and stomach. More importantly, [21]the sun also provides us with our main source of 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 to get 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 us with 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?
正確答案：D
解析：老師在承認(rèn)長時間曬太陽的害處后強(qiáng)調(diào)的是其益處，答案為D。說法過于絕對的選項(xiàng)不能選，可直接排除B。另外有悖常識的選項(xiàng)一般也不能選，可排除C。
20. What kind of cancer may the sunlight protects us from?
正確答案：A
解析：A是老師提到陽光可以防御癌癥后列舉的例子之一。B是曝曬導(dǎo)致的。
21. What is the main function of sunshine when concerned with our bodies?
正確答案：B
解析：B為兩次提及的明示信息，特別是最后重申時應(yīng)該重視。A只是男士的一種感受。Vitamin D屬于對話后半段的高頻詞匯，往往就是答案。