I'mnotsureofthereasonforthedog'sillness,butit

問題詳情：

I'm not sure of the reason for the dog's illness, but it ________ (cause) by eating too much.

【回答】

may/might have been caused　句意：我不能肯定*生病的原因，但它也許是因為吃得太多了。根據前句“I'm not sure of the reason for the dog's illness”可知，這裏為不肯定的推測，故用may/might have done “可能做某事”；由於dog's illness與cause之間為被動關係，故*為may/might have been caused。

知識點：虛擬語氣與情態動詞

題型：閲讀填空