备考软件破解p2第69题求助！！

Sixty-five million years ago, according to some scientists, an asteroid bigger than Mount Everest slammed into North America, which, causing plant and animal extinctions, marks the end of the geologic era known as the Cretaceous Period.

(A) which, causing plant and animal extinctions, marks

(B) which caused the plant and animal extinctions marking

(C) and causing plant and animal extinctions that mark

(D) an event that caused plant and animal extinctions, and it marks

(E) an event that caused the plant and animal extinctions that mark

答案是E，解释中说D的it优先指代主句中的asteroid

这不是违背了就近指代的原则吗？岂不是只要前面出现过两个以上的名词，后面就一律不能出现代词，否则都会指代不明？

另外，E中的that不是应该指extinctions吗？但是原句的意思是"this event" marks the end of...，这不是改变句意吗？

我的想法是D中it就进指代event，E中mark的用法改变句意，选D，请高手指教

我觉得D 的it 指代不明，可以指代an event，也可以认为是指代前面的 an asteroid ，所以会有歧义

而E因为mark是只能指代extinctions，如果意思是指代event的话 就应该是marks

而且意思应该是extinctionns 标志着geologic era  known。。。的结束