as的疑惑

puqiandi

1.Although she had signed a pledge of abstinence while being an adolescent, Frances Willard was 35 years old before she chose to become a temperance activist.
(A) while being an adolescent
(B) while in adolescence
(C) at the time of her being adolescent
(D) as being in adolescence
(E) as an adolescent
答案是E，当初在B和E中忧郁，后来想到as后面要句子所以选了B，这里as做何解呢？ 还有B为何错？

yawgamoth86

while in 表示持续性的动作
而句子前面是过去完成时
如果你要用while 则必须改为 while she was。。。。
而且 E中 adolescent和后面的activist似乎也有平行的意味