---- Is Ann knocking at the door?--- No, it ______ be Ann. She has gone to Beijing. 

Nanjing isn’t so large __________ Shanghai, however, it’s the second __________ city in East China.

—Listen! Peter is singing in the classroom! —It _____ be him. He has gone back to his hometown.

The man over there _________ be over fifty. He looks so young.

Miss Li regards all her students _______ her children.