135. 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

A: which 指代不清

B: 同上

C: and causing 和前面没有对称的对象

D: it指代不清

E: correct

为什么it指代不清,it不是就是指event吗?

为什么it指代不清,it不是就是指event吗?

it指代不清，如果指代an event的话，违反句意，句意是说extinctions mark the

end of ..era， 不是an event.

我觉得不是it指代不清的问题，而是逻辑意思的问题。

逻辑意思是，extinctions mark。

我觉得是并列的问题，是一个同位语名词无法和句子并列。

不理解为什么Event作为标志逻辑有问题