1、Could you please help me?你能帮助我吗?
2、I couldnt come over to give you a hand.我不能过来帮助你。
3、A:——There is a man.Could it be Tom?那儿有个男子。可能是汤姆吗?
B:——It couldnt be Tom .He has gone to Beijing yesterday.不可能是汤姆。他昨天已经去北京了。
4、Jack said he could finish the work all by himeself.杰克说,他靠自己完全能够完成这项工作。