请教:PREP中的一道逻辑题

PREP破解版pratice1中CR－21：

21.   (28551-!-item-!-188;#058&003690)

Traces of cultivated emmer wheat have been found among the earliest agricultural remains of many archaeological sites in Europe and Asia.  The only place where the wild form of emmer wheat has been found growing is a relatively narrow strip of southwest Asia.  Since the oldest remains of cultivated emmer wheat yet found are from village sites in the same narrow strip, it is clear that emmer wheat was first domesticated somewhere in that strip.

Which of the following, if true, most strengthens the argument?

(A) The present-day distribution of another wild wheat, einkorn, which was also domesticated early in the development of agriculture, covers a much larger area of southwest Asia.

(B) Modern experiments show that wild emmer wheat can easily be domesticated so as to yield nearly as well as traditionally domestic strains.

(C) At the time when emmer wheat was first cultivated, it was the most nutritious of all the varieties of grain that were then cultivated.

(D) In the region containing the strip where wild emmer wheat has been found, climatic conditions have changed very little since before the development of agriculture.

(E) It is very difficult, without genetic testing, to differentiate the wild form of emmer wheat from a closely related wild wheat that also grows in southwest Asia.

为什么答案D是加强呢？还没想通。

已知：1.全世界各地都发现一种麦子。

2.这种麦子的野生品种只有在南亚的一个很狭窄的区域里才有。

结论：因为最古老的种植这种麦子的地方也在这个区域内，所以这种麦子是最先在这个区域内被种植的。

问：如何能加强结论。

答：这个区域内的气候没发生过什么变化。

A：说得是另一种麦子。和原题无关。

B: 说得是产量。和原题无关。

C: 说得是麦子的营养。和原题无关。

D: 正确。气候没有变化使得种植这种麦子更容易些。加强。

E: 说得是很难区分这种麦子和另一种麦子。