21.
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.
答案为D
请nn讲讲思路吧~~~ | 
