Can vs Could: How to Use the
我们来讨论一下情态动词can和could的用法。我们都知道能用英语表达做某事的能力或可能性有多重要，但英语语法可能很棘手。
而an和could是情态助动词，用来表达一种能力、许可、请求、提供或机会。在本文中，我们将探讨can和could之间的区别，以及如何使用它们。
Can vs. Could: 使用规则
Could 是Can的过去式
动词could主要是can的过去式。但它不仅仅是can的过去式:它还有其他can不具备的功能，例如，在第一件句中，参见英语条件从句的使用
例句
She canspeak Italian very well. I couldswim, but I couldn’tride a bike when I was nine years old. You canplay with Amy after you do your homework. CouldI have some tea? CanI carry your bags? We couldgo somewhere tonight. That can’tbe true. You couldget there in time if you hurried up.表达感知动词的能力
Can和could也可以用来表示感知动词(看、听、感觉、味道、嗅觉等)的连续时态，以及理解、记住等动词。这些词分别是(see, hear, feel, taste, smell, like understand, remember)等。
例句
Canyou see the light over there? When I entered the room, I couldhear something scratching. Harry put the keys in his pocket, but now he can’tfind them. We couldn’tunderstand what the stranger was saying.表面一般的能力
作为动词can的过去式，could在过去式和间接引语中用来表达一般能力。
例句:
He said he couldget that ticket for me. When I was younger, I couldwork out for two hours without stopping.命令或要求某事
在请求、命令和句子中，使用could比can更礼貌。
例句：
Do you think you couldhelp me with this case? CanI use your phone? Couldyou do me a favour? Do the urgent task first, and then you cancheck the rest.请求允许
当然，当我们请求许可时，最好使用动词can，因为could不能用来表示同意或拒绝同意
例句：
CanI trust you? – Of course, you can. You canstay here if you want to. CanI have another cup of coffee? – No, I’m afraid you can’t.You drank too much coffee.