在图层调板中,下面关于背景图层说法正确的是()
A、可以任意调整其前后顺序
B、背景层可以进行编辑
C、背景层与图层之间可以转换
D、背景层不可以关闭层眼
参考答案:B
Deck foam systems,designed to protect cargo areas on tankers built after January 1,1975,must have a supply of foam-producing material to operate the system at its designed rate of foam production for().
A.15 minutes without recharging
B.20 minutes without recharging
C.25 minutes without recharging
D.30 minutes without recharging
元大都首先是全国的政治中心,同时又是()和()。