【单选题】
National flag should not be（卷叠）（）.
A、rolling up
B、rolls up
C、rolled up
D、roll up
查看正确答案
A、On board national flags should be hoisted when the sun sets. B、On board national flags should be hoisted when the sun rises. C、On board national flags should be lowered when the ship is in port. D、On board national flags should be hoisted flag when loading and discharging
