答案 why
7.Exactly the potato was introduced into Europe is uncertain，but it was probably around 1565.
解析 考查名词性从句。句意：马铃薯被引入欧洲的确切时间是不确定的，但是大约是在1565年。根据句意when引导一个主语从句，且在从句中作时间状语。故填when。 答案 when
8. the delayed flight will take off depends much on the weather.
解析 考查主语从句。句意：延误的航班什么时候起飞很大程度上取决于天气。根据句意，需要时间概念When。 答案 When
9.I think impresses me about his painting is the colours he uses.
解析 考查名词性从句。句意：我认为他的绘画给我印象最深的就是他所使用的颜色。根据结构该空所填词汇引导主语从句，引导词是物，在其中做主语，故用what。 答案 what
10.Some people believe has happened before or is happening now will repeat itself in the future.
解析 考查主语从句。句意：有些人相信，无论以前发生过什么，或者现在发生着什么，都会在未来重现。主语从句中缺少主语，用whatever做主语。 答案 whatever
11. The pandas are very dear to human beings.So people have been doing they take to save them.
解析 考查宾语从句。熊猫对人类来说很宝贵，因此人们一直在做任何需要做的事情来保护它们。whatever引导宾语从句，表示“无论什么”，相当于anything that。
答案 whatever
12. To tell the truth， you do rather than what you say matters.
解析 考查主语从句。说实话，是你所做的而不是你所说的真正起作用。rather than连接的并列主语从句，主语从句均缺宾语，所以用what。
答案 what
13. What the government cares about most is action they are going to take.
6
答案 what
14. I need to put a cross on the map to show that famous hotel is. 解析 考查宾语从句。我需要在地图上放个十字来表明这个饭店的位置。 答案 where
15. We've got to remember this group wants to look at how the Internet is being used in the classroom.That's they are coming for.
解析 考查表语从句的引导词。这就是他们为什么而来。what在表语从句中作介词for的宾语，for what相当于why。
答案 what
16. Her smile just melted me and almost instantly gave me a completely new sense of life is all about.
解析 考查宾语从句的引导词。介词of后为宾语从句，从句中about缺少宾语，故要用what。 答案 what
17. Therefore，it is advisable you should value and treat them with care. 解析 考查主语从句的引导词。it为形式主语，真正的主语为后面that引导的主语从句。 答案 that
18.When the other frogs saw a deep pit it was，they told the two frogs that they were as good as dead.
解析 考查宾语从句的引导词。saw 后面接的句子是感叹句，用what引导，what a deep pit it was！多深的一个坑啊！
答案 what
19. Then they had to know stories could be told without words， using only gestures and expressions.
解析 考查宾语从句的引导词。由结构可知此处是宾语从句，根据stories could be told without words, using only gestures and expressions.可以判断出，此处指如何去做到这一点。
答案 how
20. His teacher got the idea that he had no ability in arithmetic，and told his parents she thought in order that they would not expect too much of him.
7
答案 what
8