The book you want is not ___now. I will let you know as soon as it is returned to the library.

A．useful

B．possible

C．available

D．practical

（）进出我国港口，不适用于我国船舶签证管理规则。

A.国内航行船舶

B.港内航行的港作船

C.国际航行船舶

D.国内从事营业性运输的部队船舶