[問題]PPtest2-Q113(sturcture)

[ministar]

PPtest2 Q113

That brought about the widespread extinction of the dinosaurs is unknown; it must, however,
have involved major changes in the enviroment.

Ans:A

我知道A錯了 但是D也很怪
因為前面主詞是it D後面不是就該改成has invoved???
為什麼D這樣是對的阿

拜託大大幫我回答一下喔 先謝謝囉

[oddesy]

it must have ivolved
must是助動詞