句型It is …… that ……
I want to go to America this summer.
It is America that I want to go to this summer.
全部倒装：There be 句型 + n + 介词短语
现在 There is a book on the table.
not、no、never、hardly、little、scarcely、seldom、not until、not only……
I will never do it.
never will I do it.
|假设过去||had done||would +have done|
were to do
|might + do|
If I were to have/had/should have time tomorrow, I would help him.
If you had married him, you would be the wife of a gas station attendant.
if you had joined us, we would have had more fun.
had you joined us, we would have had more fun. (部分倒装)
He suggested that the system should be changed.