单选题 Here is a new idea in agricultural weed control. Rather than trying to formulate herbicides that kill specific weeds but are harmless to grain crops, use a broad-spectrum herbicide effective against all kinds of plants and use genetic engineering specifically to make the crops impervious to the herbicide.
Which of the following, if true, is the most serious obstacle to an implementation of the new idea outlined above?

A、 Certain herbicides that are effective against specific weeds can inhibit the growth of certain crops as much as two years after application.
B、 Research to date suggests that the nutritional properties of crop plants would not improve as a result of the genetic alterations being contemplated.
C、 Most herbicides that kill only a narrow range of targets contain active ingredients that are harmful to domestic animals and wildlife.
D、 Effective broad-spectrum herbicides are on the market, but their very effectiveness has so far rendered them unsuitable for agricultural weed control.
E、 (E) Although genetic modification has made individual plants of grain species resistant to broad-spectrum herbicides, the seeds that such plants produce will not sprout.

【正确答案】 E

【答案解析】[解析] 要解答本题，就是要找一个选项说明新的除草剂不可行。(E)选项指出，虽然通过基因工程能使农作物不受除草剂的伤害，但是农作物的种子会因为万能除草剂的作用而不会发芽。种子不会发芽，该作物物种就要灭绝。(E)选项从而否定了新的除草剂的可行性，所以(E)正确。(D)容易被误选，选(D)的人会认为人们不信任这种新的万能除草剂肯定就是新的除草剂被实施的障碍，但是应注意的是人们只是在这种万能除草剂刚上市时，对它有这种不信任的态度，但是随着时间的推移，当万能除草剂的独特性能表现出来时，人们肯定就会争相购买，而选项(E)则指出了万能除草剂内在的致命缺陷，因此(E)是正确答案。