What you are going to do is （to） give him a lesson. 為什麼是 is give 而不是 is to give?

來自專欄英語思維 解密語法的原理

What you are going to do is to give him a lesson. 為什麼是 is give 而不是 is to give?

上句相當於：

what is to give him a lesson.

把what引導的主語從句換成一個單個名詞：

Your job is to give him a lesson.

to give him a lesson就是一個不定式做表語。

附國外網站的問答：

Which sentence below is correct and why is the other one incorrect?

All I have to do now is get the report from the teacher.

All I have to now is to get the report from the teacher.

Do I need to write "to" in front of "get", both sounds correct to me but I know one of them is wrong.

答：

Yes, those are the three situations where you have a choice of to or no to:

1. all subjects,
2. what subjects,
3. and subjects containing an ordinal or a superlative (first, best, next etc.).

They can all be said both ways.

例句：

1. 1.

What we are going to do is to continue to engage internationally with Iran.

CNN: SHARE THIS

1. 2.

"What we are going to do is to challenge people to say why they are not going to assume that life expectancy is going to carry on improving" said Mr Norgrove.

BBC: Warning on pensioners longevity

1. 3.

And one of the things were going to do is to help Americans once again face the future with security and have a retirement plan that really helps middle-class Americans.

CNN: Clintons October 9, 2007 speech on retirement security

1. 4.

And so I think what the President is going to do is to put in place the best that we can, working with Congress, and then see if we can get better performance.

WHITEHOUSE: Press Briefing

1. 5.

But what Im not going to do is to extend Bush tax cuts for the wealthiest 2 percent that we cant afford, and according to economists, will have the least positive impact on our economy.

WHITEHOUSE: President Obama Holds a Press Conference

如果尚未發生，建議用to;

如果馬上就要發生/即將發生/就是現在，可以省略 to

如：

All you have to do now is listen.