选择合适的应答语。
（  ）（1） What is he doing?
（  ）（2） Is it cold?
（  ）（3） Are they happy?
（  ）（4） What are they doing?
（  ）（5） May I come in ?

A．Please come in .

B．He is flying a kite.

C．They are singing .

D．Yes , it is .

E. No , they are not happy.