prep 1#194 in comparison

194.
            (28686-!-item-!-188;#058&003293)

Whereas the honeybee’s stinger is heavily barbed and cannot be retracted from the skin, because the yellow jacket has a comparatively smooth stinger, it is therefore able to be pulled out and used again.

A. because the yellow jacket has a comparatively smooth stinger, it is therefore able to be pulled out and used

B. the comparative smoothness of the yellow jacket’s stinger allows them to pull it out and then can therefore use it

C. the yellow jacket’s stinger is comparatively smooth, and can therefore be pulled out and used

D. in comparison, the yellow jacket’s stinger is smooth, and thus able to be pulled out and used

E. in comparison, the yellow jacket has a smooth stinger, thus allowing it to be pulled out and used

并列平行：whereas 句的主语与主句主语要尽量保持平行，所以只剩下CD，D为什么不对呢？