should 与could有什么区别,具体说明
以下有几个句子看是用should还是用could写解析
You could/should write him a letter.
You could/should call him up.
You could/should say you're sorry.
You could/should go to his house.
You could/should give him a ticket to a ball game.
这是书上的答案分别是could,should ,should ,could,could。请写出怎样区分它们的思路,谢谢谢谢