原句:

Although the development of science and technology has brought the process to mankind, our surrounding natural environment is greatly destroyed.

改句:

The development of science and technology has brought the process to mankind whileour surrounding natural environment is greatly destroyed.

【解析】

原句是一句典型的转折句，在四六级作文中，"although"和"though“的应用相当广泛，那么如何使自己与众不同呢，在此，我为大家推荐一个连词”while“，这个单词有很多意思，但在改句中，它的意思是”虽然、尽管“，在考场上用的人相对比较少，所以以后在作文中，如果出现了转折、对比之类的关系句，记住要想到”while“哦！

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Existing employees have made concessions, such as higher retirement ages, but it is near impossible to reduce the payments made to existing pensioners.

答案：

While existing employees have made concessions, such as higher retirement ages, it is near impossible to reduce the payments made to existing pensioners.