GWD17-Q38（对比大全一题） 关于时态，战友们帮忙！

Avatar800

All Y chromosomes in existence today are descended from a single ancestor’s who is thought to have lived about 140,000 years ago.



A.a single ancestor’s who is thought to have lived

B.a single ancestor’s who was thought to live

C.a single ancestor whom it is thought had lived

D.the Y chromosome of a single ancestor who is thought to have lived

E.the Y chromosome of a single ancestor whom it was thought had lived



请教大全157

157.Balzac drank more than fifty cups of coffee a day and died of caffeine poisoning; furthermore, caffeine did not seem to bother Samuel Johnson, the great writer and lexicographer, who was reported to have drunk twenty-five cups of tea at one sitting.
(B) however, caffeine did not seem to bother
(C) however, caffeine did not seem to have bothered

绿色标出的为正确答案，这两道题我真无语......................

姿姿不倦

唔.虽然我第一题也是错的.但是我发现第一题的D和第二个题目题干的一句结构好像啊。。
the Y chromosome of a single ancestor who is thought to have lived
who was reported to have drunk twenty-five cups of tea at one sitting


看到另一个帖子有TX说:
be thought/known to have done是一个好的表达，表明done的事情发生在过去，并不是表示完成。举个例子：

如果用It is known造句：It is known that Edison invented electronic light bulbs in 2000.

如果把这个句子改称be known to的形式就要用: Edison is known to have invented electronic light bulbs in 2000.
地址在http://forum.chasedream.com/GMAT_SC/thread-363418-1-1.html

Avatar800

见过此帖，但不认为这种说法合理，况且第二题的题干那句和第一题的D还是又差别的，was和is没有影响么？再求解~

姿姿不倦

who is thought是 现在被认为啊 所以用is
was reported是过去被报道过么。
不过我说这两个好像纯粹是觉得凑巧。。小发现。。和这个解题无关啦哈哈。。

红尘道士

http://forum.chasedream.com/GMAT_SC/thread-91380-1-1.html
这个帖子讲的很清楚

红尘道士

根据上面帖子的说法
the Y chromosome of a single ancestor who is  thought to have lived
是别人的看法，不是作者的看法
however, caffeine did not seem to bother
是作者自己的看法
who was reported to have drunk twenty-five cups of tea at one sitting

是别人的看法，不是作者的看法

Avatar800

万分感谢，很清楚了~~~~~~~~~~~~~

妞wq090709

c为什么不对