(1) cannot help doing “不能不、禁不住”,如:I couldn’t help thinking about the past.(我禁不住想起过去的事。)
(2)cannot but do (=cannot help but do),如:Talk to the guy for five minutes, and you can’t help but like him.(去和那个人聊上五分钟,你也会禁不住喜欢他的。)
(3)have no choice but to do(=can’t choose but do),如:We had no choice but to destroy the animal.(我们别无选择,只好杀了这只动物。)