89. Rhizobium bacteria living in the roots of bean plants or other legumes produce fixed nitrogen, which is one of the essential plant nutrients and which for non-legume crops, such as wheat, normally must be supplied by applications of nitrogen-based fertilizer. So if biotechnology succeeds in producing wheat strains whose roots will play host to Rhizobium bacteria, the need for artificial fertilizers will be reduced.

The argument above makes which one of the following assumptions?

A.     Biotechnology should be directed toward producing plants that do not require artificial fertilize.

B.      Fixed nitrogen is currently the only soil nutrient that must be supplied by artificial fertilizer for growing wheat crops.

C.     There are no naturally occurring strains of wheat or other grasses that have Rhizobium bacteria living in their roots.

D.     Legumes are currently the only corps that produce their own supply of fixed nitrogen.

E.      Rhizobium bacteria living in the roots of wheat would produce fixed nitrogen.

 参考答案：E
思路：原文的结论是“如果生物工程可以成功培育出能寄生根瘤菌的小麦品种，对人工肥料的需求就会减少”；“生活在大豆或其它豆科植物根部的根瘤菌产生固氮（一种重要的植物养份）”是结论的major premise，应该在二者之间搭桥建立联系，即小麦上寄生的根瘤菌同样能产生固氮。

各位牛牛，b项不可以吗？如果人工肥料不仅仅提供氮，也提供可能对小麦生长也有作用的其他养分，那即使实验成功，也无法彻底抛弃人工肥料啊

结论并不是" the need for artificial fertilizer is no longer existed"
而是" reduced"

就算there are other nutrients that must be supplied by artificial

fertilizer. 因为 fixed nitrogen 至少不用supply 了， 所以还是reduce, 结论没

有被削弱。。。