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As question tags são perguntas curtinhas no final de uma frase, pedindo uma confirmação.

– Quando esperamos uma resposta negativa, usamos uma frase negativa e a question tag na forma afirmativa:

You don’t want to do that, do you?
He can’t go there, can he?
She wasn’t supposed to come, was she?

– Quando esperamos uma resposta afirmativa, usamos uma frase afirmativa e a question tag na forma negativa:

You want to do that, don’t you?
She can speak German, can’t she?
They were supposed to come, weren’t they?

– Quando a frase principal tem um verbo auxiliar, o mesmo verbo auxiliar é usado na question tag:

They are English teachers, aren’t they?
You have always lived here, haven’t you?
You can hear me well, can’t you?

– Quando a frase não tem um verbo auxiliar na frase principal, então a question tag vai conter do, does ou did:

You work in a factory, don’t you?
You don’t work in a factory, do you?

He works as a waiter, doesn’t he?
He doesn’t work as a waiter, does he?

You worked there for many years, didn’t you?
You didn’t work there for many years, did you?

– O sujeito da question tag é sempre um pronome – ou there quando a frase principal começar com there is, there are etc. – mas nunca um substantivo:

This bar is crowded tonight, isn’t it?
There’s a drugstore around the corner, isn’t there?

Casos Especiais

– Quando a frase principal começa com I am, a question tag é aren’t I?;

I’m stronger than you, aren’t I?
I’m bothering you, aren’t I?

– Quando a frase principal começa com Let’s, a question tag é shall we?;

Let’s start work now, shall we?
Let’s not argue over that, shall we?

– Frases imperativas – afirmativas ou negativas – se tornam mais polidas acrescentando-se a question tag will you?;

Turn down that radio, will you?
Don’t open the window, will you?

– Palavras negativas tais como never, nothing, nobody, etc tornam a frase negativa então a question tag correspondente é afirmativa.

Mary’s uncle never comes late, does he?
Nothing’s going to change, is it?
Nobody showed up, did they?