could的四种用法：作为情态动词，意为“能”；委婉的提出问题或陈述看法；用于条件句和假设句的主句中；与过去分词连用，表示现在对过去事物的判断。could可作情态动词和动词，含义有可以、把…装罐保存、炒…的鱿鱼等。
could的基本含义及用法介绍
1、作为情态动词，是can的过去时，意为能、可以。
例句：She said that she couldn't come.
她说她来不了啦。
I couldn't hear what they were saying.
我听不见他们在说些什么。
Could I use your phone, please?
请让我用一下你的电话可以吗？
Could you babysit for us on Friday?
你星期五帮我们看一下孩子好吗？
I could do it now, if you like.
如果你愿意的话，我现在就可以做这事。
We could write a letter to the director.
我们不妨给主管写封信。
They could have let me know they were going to be late!
他们要晚来，也该早告诉我一声呀！
I'm so fed up I could scream!
我烦透了，非大喊大叫不可！
I could have won the game but decided to let her win.
我本可以赢得那场比赛，但还是决定让她赢了。
We weren’t able to/didn’t manage to/couldn’t get there in time.
我们未能及时赶到那儿。
She’d love to be able to play the piano.
她很希望能弹钢琴。
Our daughter could walk when she was nine months old.
我们的女儿九个月大就会走路了。
2、作为动词，意为把(食品)装罐保存;让…卷铺盖走人;炒…的鱿鱼。
