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.
这个题目。。。正确答案是D，可是我真的没有搞明白D的逻辑？？甚至连意思好像都不太明白？解释一下吧~谢谢了
GWD1-Q40:
Until mow, only injectable vaccines against influenza have been available.
arents are reluctant to subject children to the pain of injections, but adults, who are at risk of serious complications from influenza, are commonly vaccinated. A new influenza vaccine, administered painlessly in a nasal spray, is effective for children. However, since children seldom develop serious complications from influenza, no significant public health benefit would result from widespread vaccination of children using the nasal spray. Which of the following is an assumption on which the argument depends?
A. Any person who has received the injectable vaccine can safely receive the nasal-spray vaccine as well.
B. The new vaccine uses the same mechanism to ward off influenza as jnjectable vaccines do.
C. The injectable vaccine is affordable for all adults.
D. Adults do not contract influenza primarily from children who have influenza.
E. The nasal spray vaccine is mot effective when administered to adults.
正确答案是D，我把选项带进去，难道文章的逻辑是:因为大人不给小孩注射，而成人没有被小孩感染（D），所以，医疗机构得不到好处？是这样的吗？？
-- by 会员 水色青空 (2010/2/6 21:48:27)
