Linda’s aunt looks _younger than she is.In fact she is_over fifty.

Linda’s aunt looks _younger than she is.In fact she is_over fifty.
A)much,very B)much,well C)more,quite D)more,rather 答案是B可是为什么要用well,is不是系动词么,那么应该要用形容词,还有over fifty是介宾短语,介宾短语是不是相当于形容词啊?