闭路电视监控系统系统的供电电源应采用220V、50Hz的单相交流电源，并应配置专门的配电箱。当电压波动超出（）时，应设稳压电源装置。

A.-10%～+5%

B.-10%～-5%

C.+5%～+10%

D.-10%～0

Which space cannot be deducted from gross tonnage when calculating net tonnage（）.

A.Crew messroom

B.Forepeak ballast tank

C.Master's cabin

D.Chain locker