求解一题GWD1-Q15

yuki_real

GWD1-Q15:

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?

A.The growing conditions required by the varieties of sweet potato currently cultivated in the region are conditions in which SPK004 can flourish.

B.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.

C.There are no other varieties of sweet potato that are significantly richer in beta-carotene than SPK004 is.

D.The varieties of sweet potato currently cultivated in the region contain some important nutrients that are lacking in SPK004.

E.There are other vegetables currently grown in the region that contain more beta-carotene than the currently cultivated varieties of sweet potato do.
答案选a，为什么c不对呢？