can与be able to在作“能够、会”解时,它们的区别在于:
can没有将来式和完成式,因此,当用在shall、will、have后面时,要用be able to。
例句:She has not been able to get home before dark.
她没能在天黑前赶回家。
can与be able to不能重叠使用。
例句:I can finish the job.正确
I am able to finish the job.正确
I can be able to finish the job.错误
我能完成那个工作。