请教刘振民上有关so...as to和so...that的一道题

The Emperor Augustus, it appears, commissioned an idealized sculptured portrait, the features of which are so unrealistic as to constitute what one scholar calls "artificial face".
A. so unrealistic as to constitute
B. so unrealistic they constitute
C. so unrealistic that they have constituted
D. unrealistic enough so that they constitute
E. unrealistic enough so as to constitute

答案是A。我的疑问是，so...as to不是要求用在同一套主谓的情况下吗，这里的主语虽然是一个，但是谓语一个是be一个是constitute啊。。。

C选项中不应该出现完成时，但是如果C选项改为so unrealistic that they constitute是否就比A好了呢？
---即使改成你写的，我估计这题目还是会选择A，A要简洁
请大家帮忙，谢谢。