作者：英吉
Paleontologists believe that fragments of a primate jawbone unearthed in Burma and estimated at 40 to 44 million years old provide evidence of a crucial step along the evolutionary path that led to human beings.
(A)at 40 t0 44 million years old provide evidence of
(B) as being 40 t0 44 million years old provides evidence of
(C)that it is 40 t0 44 million years old provides evidence of what was
(D)to be 40 t0 44 million years old provide evidence of
(E)as 40 t0 44 million years old provides evidence
题目分析：believe后面引导了一个宾语从句，从句中的主语是fragments但是后面没有马上跟谓语（这个时候我就知道有可能要考主谓是否一致，这些插入成分无非是把主语和谓语之间在距离上隔开一些。）fragments是复数，provide用单数显然不合适，我们先干掉B，C和E。A和D进行比较，唯一的差异就是一个用at一个用to be，到底用哪个取决于划线外的estimated，这个词语义上表达的是估计有44 million这么老的意思，at表示现有状态，比如the two countries are at war，这句话的意思就是两个国家正在交战，而to be强调的是前后关系，表达的意思是估计有44 million这么老的意思，不是现有状态，是估计的状态，而确实应该是先估计，之后得出有44 million这么老的这么一个结论，所以to be比at表达的意思更为合理，选D。
