No, you're not. Come in. Are you laughing or crying? ~ Crying, mainly. This book is very sad. Is it upsetting you? ~ Yes, it is. But I want to finish it. Do you have English lessons on Saturdays?

We can reply to tag questions either with simple yes/no answers (negative tags normally expect a yes answer and positive tags normally expect a no answer) or by using yes/no + auxiliary verb.