GWD1-Q33:

A company plans to develop a prototype weeding machine that uses cutting blades with optical sensors and microprocessors that distinguish weeds from crop plants by differences in shade of color.  The inventor of the machine claims that it will reduce labor costs by virtually eliminating the need for manual weeding.

Which of the following is a consideration in favor of the company’s implementing its plan to develop the prototype?

A.      There is a considerable degree of variation in shade of color between weeds of different species.

B.       The shade of color of some plants tends to change appreciably over the course of their growing season.

C.      When crops are weeded manually, overall size and leaf shape are taken into account in distinguishing crop plants from weeds.

D.      Selection and genetic manipulation allow plants of virtually any species to be economically bred to have a distinctive shade of color without altering their other characteristics.

E.       Farm laborers who are responsible for the manual weeding of crops carry out other agricultural duties at times in the growing season when extensive weeding is not necessary.

Why is D?

D 排除他因，从而支持：只要通过shade of color 判断即可

C是weaken：手工还要通过其他方式判断，那明显说机器判断没有手工精确，那机器不就不好了嘛

觉得楼上的分析还有些不到位，修正及补充一下：

C）我觉得这个选项是不相关的。手工除草时农民可以用其他更适合肉眼和人脑的方式来进行区分，但跟机器应用哪种方式并没有什么关系。比如人可能更适合用形状来判断而机器适合用颜色来区分。

D）这个选项的直接意思是：基因工程或者人工选种的方式可以让任意植物的颜色区分于其他植物。而隐含的意思是你们不用担心农作物和杂草的颜色会区分不出来。所以对论点是一个很正面的支持作用。