这题没想通呐 @_@

E中的not likely 根本就是错的嘛~~ 为什么不能选A呢？？

谁提到过not likely是错的？转折句前后的句子要对等，像a那样用一个逻辑主语的就不是简洁的用法，而且你把a项还原： that its effect on their size is significant is unlikely ，正确吗？

给出longman关于likely的解释

unlikely adjective
1
not likely to happen
Donna might be able to come tomorrow, but it's very unlikely .
unlikely to do something
The weather is unlikely to improve over the next few days.
it is unlikely (that)
It's unlikely that the thieves will be caught.
in the unlikely event of something (=if something which is unlikely happens) In the unlikely event of a fire, passengers should move to the top deck.
2
an unlikely place, person, or thing is strange and not what you would expect
The quiet village of Brockhampton was an unlikely setting for such a crime.
3
not likely to be true
an unlikely story