A．单句填空
1．Exactly________the potato was introduced into Europe is uncertain, but it was probably around 1565.
答案 when [句意：马铃薯具体是在什么时候被引入欧洲的并不确定，但有可能是在1565年左右。由句意可知，后一分句是来补充说明前一分句中的不确定的内容的，根据“around 1565”可知是对时间进行提问，因此用when引导前面的主语从句。]
2．I think________impresses me about his painting is the colours he uses.
答案 what [句意：我认为他的画给我印象最深的是他对色彩的运用。what引导主语从句，且在从句中作主语，表示“……的”。]
3．Some people believe________has happened before or is happening now will repeat itself in the future.
答案 what/whatever [句意：一些人认为，不管是以前发生的还是现在发生的事情都会在将来重现。此处“________has happened before or is happening now”是主语从句，且从句中缺少主语，故填what/whatever。]
4．________the delayed flight will take off depends much on the weather.
答案 When [句意：延误的飞机何时起飞很大程度上取决于天气状况。根据句意填连接副词When。]
5．________makes the book so extraordinary is the creative imagination of the writer.
答案 What [句意：使这本书非同寻常的是这位作家创造性的想象力。What在此处引导主语从句，并在从句中作主语。]
6．________you are on good terms with your classmates will affect your mood.
答案 Whether [句意：你与同学相处得是否融洽会影响你的情绪。此处为主语从句，if表示“是否”且于句首时不引导主语从句。根据句意可知应用Whether。]
7．It suddenly occurred to me ________I hadn't locked my door.
答案 that [句意：我突然想起我没锁门。it是形式主语，真正的主语是that引导的从句。It occurs to sb. that意为“某人突然想起……”。]
8．As the spokeswoman said，________we should take action against them depends on what they will do.
答案 whether [句意：正如女发言人所说的那样，我们是否应该针对他们采取行动取决于他们将会怎么做。本空需要用连接词引导主语从句，表示“是否”，因此用whether引导。]
9．—What made her so happy?
—________her son passed the college entrance examination.
答案 That [句意：——是什么使她这么快乐？——她儿子通过高考了。答语为that引导的主语从句，引导词在从句中不作任何成分，只起连接作用。]
10．________will matter is not how many books you read, but how much you learn when you finish reading them.
答案 What [句意：重要的不是你读了多少书，而是你读完书后学到了多少。从句子结构看，is前面是一个主语从句，从句中缺少主语，应用What。]
B．单句改错
1．That you said at the meeting describes a bright future for the company.
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答案 That→What [句意：你在会上所说的话描述了公司的光明前途。分析句子结构可知，引导主语从句，且在从句中作宾语，故用What, That引导主语从句，在从句中不作成分。]
2．It remains to be seen that the newly formed committee's policy can be put into practice.
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答案 that→whether [句意：这个新成立的委员会的政策能否实施还有待观察。分析句子结构可知，It 作形式主语，而真正的主语是后面的从句“that the newly formed committee's policy can be put into practice”；再根据句意可判断，此处表示“是否”，故改为whether, that无意义。]
3．It struck me most in the movie was the father's deep love for his son.
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答案 It→What [句意：这部电影最打动我的是父亲对他儿子深深的爱。“It struck me most in the movie”为主语从句，从句中缺少主语，表示“所……的”，故用What，It不引导从句。]
4．Which one of you breaks the window will have to pay for it.
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答案 Which→Whichever [句意：你们中任何一个人打破窗户都必须赔偿。根据题干中one of you可知，空处要用whichever修饰one, 指“你们中的任何一个人”。which指哪一个，表达疑问，故改为whichever。]
5．It doesn't matter how many times you fail; that matters is how many times you stand up and try again.
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答案 that→what [句意：你失败多少次都不要紧；要紧的是你有多少次站起来并再次尝试。分析句子成分可知，“that matters”是主语从句，从句中缺少主语，指物，故用what引导。that不作成分。]
6．We have learned from the story that which is most valuable is not what we have in our lives but who we have in our lives.
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答案 which→what [“which is most valuable”是主语从句，在宾语从句中作主语，根据语境可知，该主语从句缺少主语且表示事物，故用what。which指某一范围中的哪个或哪些。]
7．It was never clear that the man hadn't reported the accident sooner.
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答案 that→why [句意：不清楚这个人为什么不早一点报告那起事故。此处需要连接副词引导主语从句并在从句中作原因状语，why表示“为什么……”。故把that改为why。]
8．—The manager finally agreed to our new marketing proposals.
—It never occurred to me what you could succeed in persuading him to change his mind.
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答案 what→that [答句表示“我根本就没想到你能说服他改变自己的看法”，句中It作形式主语，这里应该用that引导主语从句，连接词在从句中不作任何成份，也无意义。故把what改为that。]