could,was able,managed to,succeedin的区别

can/could:指的是人本身所具有的能力,一般的能力
be able to ：指的是具体做成某件事的能力
All the people were able to escape from the fire in time.这里就不能用can/could
manage to do:设法做成某事,有try to do sth.的意思,但是有成功的结果.
try to do:只说尽力去做,但没有成功与否的结果.
succeed in doing sth.成功地做成了某件事=manage to do