49. --- Does he study very hard at school?

--- Yes, he studies _____.

A．very indeed hard

B．hard very indeed

C．very hard indeed

D．indeed very hard

钻台紧急呼叫的联络信号采用（）的方式联络。

A.连续长音；

B.连续短音；

C.间断短音；

D.间断长音。