I just wanted to understand if the below sentence has any grammatical error. This might logically not be right though.

Although she had signed a pledge of abstinence at the time of her being adolescent, Frances Willard was 35 years old before she chose to become a temperance activists.


Question
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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

OA is E.