2)说话人对宾语的兴趣大于对主语的兴趣。
例2 The books are written especially for children.(说话人关心的只是;这本书是特别为孩子们准备的。目的达到就行，书的作者是谁不用管他)
3)不愿意说出动作的执行者，目的是为了使语言更加圆滑、得体。
例3 It’s generally considered impolite to ask one’s age，salary，marriage，etc.(这句话的潜语境是，有人不识时宜地询问别人的年龄、收入和婚姻状况等，而这是非常不礼貌的。本句的说话者为了避免交际陷入尴尬刻意略去了主语，而选择了"It"作形式主语)
4)出于修饰的原因，或使句子安排更加合理。
例4 The professor came to our school and warmly welcomed by the teachers and students.(句子的后半句用被动式就可以只安排一个主语"the professor"。)
汉语虽然也有"被"、"由"之类的词表示动作是被动的，但这种表达远没有英语的被动语态那么常见。因此，很多英语被动句在翻译时就被译成了汉语的主动句。反之，很多汉语的主动句在译成英文时会变成英语被动态。
Exercise Eight
1. _______________ (随着工商业的发展),the number of trees in many big cities has dramatically reduced.
2. Travel can widen our knowledge, _____________ (扩大我们的眼界),and make one open-minded as well.
3. Cars are responsible for most of the smog in cities, _______________ (这已经对环境造成了严重的污染).
4.Modernization will be entirely possible in the first half of the 21st century, as long as we ________________(坚持认为)that economic development is the center of all our work.
5. He was convinced on the basis of ____________(当时已出现的情况)that there would be a long and difficult struggle.
答案解析：
1. With industries and business developing quickly
解析：本句意为：随着工商业的发展，许多大城市的树木数量正急剧减少。"随着......"要用介词with或along with。"工商业"既包括工业也包括商业，翻译时要注意译文的完整性。本句也可译成：With the quick development of industries and business.
2. broaden our horizon
解析：句中的短语widen our knowledge意思是"扩大我们的眼界"，make one open-minded是同义复指，它们表示相同的意思却在英语里使用不同的表达，以避免用词重复。这是英语行文的一个技巧，考生在翻译时应尽量避免 wordiness(用词累赘)，这个技巧在写六级作文时也值得借鉴。本句还可以译成：expand our vision或extend our sight.