The answers:

(1)    He ......... is ........... a teacher.

(2)    They ..... are .......... friends.

(3)    I ........... am ........... a nurse.

(4)    You ...... are  .......... a student.

(5)    We ........ are ........... happy.

(6)    It ........... is ............. a tree.

(7)    She .........is ............. a doctor.