Is he thin? (Affirmative form)
Yes, he is.
Are ____ a student? Yes, I am.
you
Are you a doctor? (Negative form)
No, I'm not.
Is Helen sad? (Affirmative form)
Yes, he is.
Are they hungry? (Negative form)
No, they aren't.
Is it tired? (Negative form)
No, it isn't.
Is she hungry? (Affirmative form)
Yes, she is.
Is she your friend? (Affirmative form)
Yes, she is.