做了三次都还错，把我打醒吧

bunnyfdu2015

In parts of South America, vitamin-A deficiency is a serious health problem, especially among children.In one region, agriculturists are attempting to improve nutrition by encouraging farmers to plant a new variety of sweet potato called SPK004 that is rich in beta-carotene, which the body converts into vitamin A.The plan has good chances of success, since sweet potato is a staple of the region's diet and agriculture, and the varieties currently grown contain little beta-carotene.

Which of the following, if true, most strongly supports the prediction that the plan will succeed?

	The growing conditions required by the varieties of sweet potato currently cultivated in the region are conditions in which SPK004 can flourish.
	The flesh of SPK004 differs from that of the currently cultivated sweet potatoes in color and texture, so traditional foods would look somewhat different when prepared from SPK004.
	There are no other varieties of sweet potato that are significantly richer in beta-carotene than SPK004 is.
	The varieties of sweet potato currently cultivated in the region contain some important nutrients that are lacking in SPK004.
	There are other vegetables currently grown in the region that contain more beta-carotene than the currently cultivated varieties of sweet potato do.

选A，我一直就是AC死都搞不清楚，老师也跟我讲过，我自己不长记性，思维为什么就不能变过来啊？
我不怀疑A的正确性，是不是就是C说的是一个程度性问题，所以错...?

yuanhaowen

看清楚结论：the varieties currently grown contain little beta-carotene. 条件已经说没有这样的potato了你还说有这样的potato明显不合理对吧。

CatherineTSIM

前提是：since sweet potato is a staple of the region's diet and agriculture, and the varieties currently grown contain little beta-carotene.
结论是：The plan has good chances of success。注意：是这个计划可以成功的让人们摄取维他命A。

C选项：没有其他的甜土豆可以比SPK004含有更多的beta-carotene，我们取非以后发现，就算有其他的品种比SPK004更有beta-carotene，也只是质疑我们种不种SPK004，但是不能质疑SPK004可不可以成功达到结论。
A选项：直接影响了甜土豆能不能种成，取非以后，甜土豆不能种成了，那么计划就会失败了。所以这个是计划成功的一个重要的条件。

这样楼主明白了嘛？

bunnyfdu2015

CatherineTSIM 发表于 2014-7-19 18:01
前提是：since sweet potato is a staple of the region's diet and agriculture, and the varieties curre ...

取非了以后不能削弱，所以就错了，嗯嗯