My school teacher said that "Could I go?" is more polite than "Can I go?" but according to me "Could I go?" can not be used interchangeably but should be used as to in...
Yes, you can go.; offer to do something: Can I help you?. Statements with can. The verb can always requires the infinitive form of the following verb: She can swim. They can go. …
Could we go home now? We use can to give permission: You can go home now. You can borrow my pen if you like. We use can to say that someone has permission to do something: We …
We use can to express possibility or to question possibilities: We can go to Rome in June because both of us have a week off work. (It is …
When can we 用在疑问句中，比如 When can we go to the zoo ? 我们什么时候可以去动物园？ When we can 用在陈述句中，一般在句子中做宾语。
更多内容请点击：Can - English Grammar Today - Cambridge Dictionary