Original text:

At the age of twelve years, the human body is at its most vigorous. It has yet to reach its full size and strength, and its owner his or her full intelligence; but at this age the likelihood of death is least.

____ reached its full size and strength.

(a) It hasn't before (b) It hasn't even (c) It still hasn't (d) Yet it hasn't

答案是(c). 但是我觉得(d)也是可以的.

我的理解是否有问题？谢谢！