1. (+) I am a student.
(-) I am not  a student.
(?) Are you  a student ?
2. (+) She is tall
(-) She is not/isn't  tall.
(?) Is she tall ?
3. (+) He is 10 years old.
(-) He is not/isn't 10 years old.
(?) Is he 10 years old?
4. (+) Mary is young.
(-) Mary is not/isn't  young.
(?) Is Mary young?
5. (+) They are doctors.
(-) They are not/aren't doctors.
(?) Are they doctors?