NOS 205和319

以下是引用braveMBA在2003-5-15 23:23:00的发言：
205. His studies of ice-polished rocks in his Alpine home-
land, far outside the range of present-day glaciers,
led Louis Agassiz in 1837 to propose the concept of
an age in which great ice sheets had existed in now
currently temperate areas.

(A) in which great ice sheets had existed in now
currently temperate areas
(B) in which great ice sheets existed in what are
now temperate areas
(C) when great ice sheets existed where there were
areas now temperate
(D) when great ice sheets had existed in current
temperate areas
(E) when great ice sheets existed in areas now that
are temperate
为什么用what 从句？如果用排除法似乎只有B可以，但是为什么？

319 Bob Wilber became Sidney Bechet’s student and
    protege when he was nineteen and, for a few years in
    the 1940’s, came as close to being a carbon copy of
    the jazz virtuoso in performance as anyone has ever
    come.
    (A) as anyone has ever come
    (B) as anyone ever had been
    (C) as anyone ever had done
    (D) that anyone ever did
    (E) that anyone ever came
A是答案。as…as 比较，有三个疑问：1是COME为什么不用DONE来替换？2是感觉比较的动作应该是BE。3是是否可以根据EVER的位置和对完成时态的要求，直接选A？

不知道OG同XDF的题目之间在SC上是一个什么样的关系？请牛牛们指明。谢了