过去 I wrote emails.
I was writing the letter when he came in.
They were writing the letter when I came in.
I had written the letter yesterday.
I had been writing the letter.
现在
I write emails.
He writes emails.
She writes emails.
I'm writing the book.
She is writing the book.
You are writing the book.
We are writing the book.
I have written the letter.
I have been writing the email.
未来
We will write the email tomorrow.
We will be writing the book.
We will have written the letter.
We will have been writing the book.
虚拟语气would
We would write the email tomorrow.
We would be writing the book.
We would have written the letter.
We would have been writing the book.
虚拟语气should
We should write the email tomorrow.
We should be writing the book.
We should have written the letter.
We should have been writing the book.
虚拟语气could
We could write the email.
这句话暗示了现在或将来的可能性或建议。
We could be writing the book.
这也暗示了一个建议，但将动作置于现在进行时态。 它提出了一种现在可能发生的替代行动。 例如，如果有人感到无聊或正在寻找一些有成效的事情做，他们可能会这么说。
We could have written the letter.
这表示过去错过了机会或可能性。 演讲者正在思考哪些事情本来可以做，但没有做。
We could have been writing the book.
这句话将过去进行时与假设情况结合起来，表明在过去的某个特定时间里，他们有机会正在做某事，但没有。 它常常带有一种对如何度过时间的遗憾或事后认识的语气。
