1. After people have learned that magnets attract things, centuries passed _____ they took note of the fact that magnets sometimes also repel things.
A. before B. until C. after D. since
2. He is off to Paris again tomorrow. He tells me that, with this journey, he _____ there and back twenty times.
A. will be B. will have been
C. will go D. will have gone
3. Many ways have been found _____ small and simple machine to process large and complicated machine parts.
A. by using B. to use C. using D. used
4. I walked down the corridor, my footsteps _______ frighteningly through the empty deserted building.
A. echoing B. echoed C. to echo D. having echoed
5. Apart from personal preferences, social context also affects—both directly and indirectly---the media and the media content to which you become exposed. For example, other members of the family often select media content that you _____ , and you become ex posed to it.
A. would not have selected B. should not have selected
C. must not select D. cannot have selected
1. A before 应该理解成“（几百年过去了，人们）才……”；如果用 after 应该是…after cent uries passed they took note of the fact…；如果用 until，应该是 they didn't take noteof the fact that…until centuries passed。
2. B 此句意为：“他明天去巴黎，加上这次，他就去了二十次了。”根据句意，应用将来完 成时态。句中有 back 一词，故 D 不合适。
3. B to use…，不定式短语做 way 的定语，只是因为定语太长，故将谓语前移，使句子避免头重脚轻。by using 表示方式， 做状语用；using 为动名词，不能做 way 的定语，way 要求不定式做定语；used，无论从语法结构上还是从意义上都讲不通。
4. A 分词短语做伴随状语，my footsteps 与 echo 的关系是主动的，因此用现在分词。另外，分词做伴随状语表示与谓语动词的动作同时发生，所以用其一般式。
5. A 本句意为：“除了个人喜好外，社会环境也会直接或间接地影响你使用的媒体和媒体的内容。例如，家庭的其他成员常常选择的媒体内容你就未必选，可是你也得使用。”句中暗含了“如果是你，你就不会选”的意思，所以用虚拟语气合适。should not have selected 表示“本不应该选”；must not select 表示“一定不要选”；cannot have selected 表示“一定不能选”，过于绝对。只有 would not have selected 符合句意。
