Is Tom a doctor?yes,he is;no,he isn't
are they students?yes they are;no,they aren't
is he at school?yes,he is;no,he isn't
is this your pen?yes ,i am;no,i'm not
are these table?yes,it is;no,it isn't
Tom is not doctor
they are not students
he is not at school
this is not my pen
these are not tables