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.
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.
3. which has seriously polluted the environment
解析："这已经对环境造成了严重的污染"中的"这"显然是指前半句提到的the smog in cities，这里需要的是一个非限制性定语从句，补充说明城市烟雾对环境的影响。本句还可以译成：which has brought serious pollution to the environment。
4. hold an idea/ insist on the idea/ stick to the idea
解析：本句意为：只要我们坚持以经济建设为中心，那么在21世纪上半叶实现现代化是完全可能的。本题考查固定短语"坚持认为"的说法。除了答案提供的说法外还有以下说法大家可以参考：persist in the idea/ persevere in the idea/ adhere to the idea等。
5. what had appeared by then
解析："情况"在这里没必要直译成situation或case，本句含义是指基于当时的情况使他确信，因而可以用what引导作basis后置定语。还有一点需要注意的是，"当时已出现"要求我们在翻译时准确选择时态。by then与过去完成时态想一致，也可以用at that time。
