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.à明显的断桥
我知道E肯定是一个明显的断桥，可是对B的理解不是很透，想问问大家。B的意思是说含氮的原料是唯一需要从人工肥料中供应的，这不是一个排除他因么？如果人工肥料中还有其它的使小麦生长的养料，那么就算含氮的原料不需要了，可人工肥料的需要仍然不会减少。
想问问NN是怎么想的？ | 
京公网安备11010202008513号 京ICP证101109号 京ICP备12012021号
发表于 2005-6-2 09:20:00
楼主
