gwd21的两道问题

36. 17. GWD25-Q17（原CD16-17）

Until recently, the Inuit people led a nomadic existence, sheltering in
        igloos, the ice-block domes that are peculiar to north-central Canada,
        and in structures made of stones, bones, driftwood, and skins.

A.      Until recently, the Inuit people led a nomadic existence, sheltering

B.       During recent times, the Inuit people lead a nomadic existence,
        sheltering

C.      In the times that are recent, the Inuit people led a nomadic existence, sheltered

D.      Up until recently, the Inuit people, leading a nomadic existence, have sheltered

E.       Until recent times, leading a nomadic existence, the Inuit people
        were sheltered

答案是e ，a为什么不对

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37. GWD31-37

In 1994 the white house named Dr RuthR. Faden chairperson of the federal advisory committee of experts they assigned to do a report on the history and ethics of the government’s radiation experiments on humans in the 1950’s and 1960’s .

A.          they assigned to do

B.          to be assigned doing

C.          that was being assigned doing

D.          assigned for doing

E.          it assigned to do

答案是e， it指代什么，句子结构是什么？

GWD25-Q17:主语the Inuit people 无法 sheltering,而是被shelter（从后边看）....

GWD31-37：我觉得是advisory committee

不知道对不对。NN来指点吧