I couldn’t help but （） that it was a mistake to let him go alone.

题目

I couldn’t help but （） that it was a mistake to let him go alone.
A) think B) thought C) to think D) thinking
为什么答案选A,求解释

答案

can't help but do是个固定用法,意思是：不由得不……, 不能不.例如：
You can＇t help but respect them. 你不能不尊敬他们.
When a friend invites you to his birthday party, you can＇t help but go. 当一个朋友邀请你参加他的生日聚会, 你不能不去.
can＇t help的意思是“没有办法, 控制不了, 是没有办法的事”, 后面还可以加上it.例如：
I can’t help it if he doesn’t come. 如果他不来, 我也没办法.
其它can't help的固定搭配还有：
can＇t help doing sth. 禁不住做某事, 不由得不做某事.
can＇t help sb. doing sth. 不能使某人不做某事（某情况是无法改变的）