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?  

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

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

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

4. 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.

5. 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.

  为什么是D?E怎么错?谢啦

Ｅ怎么能说明这种机器省劳动力呢？我认为它无关
Ｄ说有一种方法能使shade of color的辨别更简单，而这种辨别正好是这种机器工作的条件。有了这种方法改

变shade of color，使这种机器更实用