To ask a yes or no question, always look at the verb. Ask yourself:
- Is the verb a modal verb (ex. can, should, would)? If yes, switch the modal verb and the subject.
Adam can sing → Can Adam sing? No, he can’t.
- Is the verb ‘to be’? If yes, switch the verb ‘to be’ and the subject.
She is dancing → Is she dancing? Yes, she is.
- Is the verb neither a modal verb nor the verb ‘to be’? Then, insert the conjugated verb ‘do’ to the beginning of the sentence.
She dances → Does she dance? Yes, she does.
They study → Do they study? Yes, they do.
Yes/no questions are negated using ‘not’ if there speaker already has an expectation of the answer.
- Can’t she swim? (I thought she could.)
- Isn’t he a doctor? (I think he is.)
- Doesn’t the dog know its name? (I assumed it did.)
