—Listen ! Helen is singing in the next room.—It __________ be Helen. She is in Tianjin now.   

— My dog is really fat.   — You______ have given it so much food. 

He _____ be really difficult at times even though he ,generally speaking, is a nice person. 

No one likes him ____. 

— I want someone to write the composition for me. 　— No! It’s a rule in our school that as a student, you _______ depend on yourself.