it is necessary that后面加什么

it is necessary that后面加从句。

例句

It is necessary that one should.

使某人必须还债。

It is necessary that he study maths.

他学数学是必要的。

It is necessary that we should master English.

我们有必要掌握英语。

It is necessary that everyone be there in time.

大家都按时到达那里是必要的。

It is necessary that we should go here at once.

我们必须立即去那儿。

It is necessary that we buy Christmas gifts now.

我们有必要现在就买圣诞礼物。