We use 'can'or'could'to say that something is possible.'Could'talks about a smaller chance than'can'.When we say that something was possible in the past,we only use 'could'.However,we cannot use'can'/'could'to talk about the chances that something will certainly happen in the future.
简单翻一下题目是什么意思
我们用 can(可以)或could(委婉的可以,也就是应该)来说什么是可能的。 could比can表示更小的几率.当我们说过去的什么是可能的,我们只用could。但是我们不能用can或could去表示一定会发生在将来的几率.顺便给楼主补充一下情态动词的知识:http://baike.baidu.com/view/190314.html?wtp=tthttp://zhidao.baidu.com/question/78602497.html?si=1&wtp=wkcan和could的用法 ■ 表示能力:能,能够,会He could swim when he was five. 他五岁时就会游泳了。Can