The boys  knock ___Uncle Wang’s door and shout “trick or treat”.

He gives them some candy___a treat.[ ]

A. on; as          

B. on; of        

C. in; as        

D. in; of

舒张期额外心音不包括( )

A．胎心样心音
B．开瓣音
C．心包叩击音
D．奔马律
E．肿瘤扑落音