Cargo vessels being navigated，and fitted with emergency lighting and power systems，shall have their emergency systems tested at least once（）.

A.a month

B.in each week

C.in every 6 months

D.in every 12 months

按照《建筑工程建筑面积计算规范》的规定，封闭式阳台( )计算建筑面积。

A．按其围护结构外围水平投影的一半
B．按其围护结构外围水平投影面积
C．一般不
D．按净面积