宏观经济学以整个社会活动作为考察对象，研究国民经济生产、分配、( )的总量、结构、运行及其变化。

A．供给和需求
B．收入和支
C．交换和消费
D．交换和需求

Ships’ masters are requested to ensure that during their call at this port , all discharging outlets are（）.

A.blockaded

B.opened

C.closed

D.enclosed