PREP中的一题句子作用题

timetoleave

27.   Plant scientists have used genetic engineering on seeds to produce crop plants that are highly resistant to insect damage.  Unfortunately, the seeds themselves are quite expensive, and the plants require more fertilizer and water to grow well than normal ones.  Thus, for most farmers the savings on pesticides would not compensate for the higher seed costs and the cost of additional fertilizer. However, since consumer demand for grains, fruits, and vegetables grown without the use of pesticides continues to rise, the use of genetically engineered seeds of this kind is likely to become widespread.

 

In the argument given, the two portions in boldface play which of the following roles?

 

(A) The first supplies a context for the argument; the second is the argument's main conclusion.

(B) The first introduces a development that the argument predicts will have a certain outcome; the second is a state of affairs that the argument denies will be part of that outcome.

(C) The first presents a development that the argument predicts will have a certain outcome; the second acknowledges a consideration that weighs against that prediction.

(D) The first provides evidence to support a prediction that the argument seeks to defend; the second is that prediction.

(E) The first and the second each provide evidence to support the argument's main conclusion.

答案是C。不知道怎么看出来的……谢谢！！！