you / my best friend? (+)
Are you my best friend? Yes, I am.
your / backpack / blue? (+)
Is your backpack blue? Yes, it is.
you / Azerbaijan? / from (+)
Are you from Azerbaijan? Yes, I am.
those / your / books? (-)
Are those your books? No, they aren't.
he / at school? (+)
Is he at school? Yes, he is.
she / Italian? (-)
Is she italian? No, she isn't.