Bài 3:
2. They aren't good friends. ( aren't là phủ định của are)
3. She isn't a doctor. ( isn't là phủ định của is)
4. I am not fifteen ( am not là phủ định của am)
5. We aren't English student ( giống câu 2)
6. You aren't from Paris ( giống câu 2)
Bài 4:
2. Are they good friends?
-> Yes, they are.
3. Is she a doctor?
-> No, she isn't
4. Are you fifteen?
-> Yes, I am
5. Are you English student?
-> Yes, we are
6. Are you from Paris?
-> No, I am not
Công thức chung: tobe + S + Object?