单项选择题
Each lifebuoy shall be marked in block capitals of the Roman alphabet with（）of the ship.
A.the call sign and name B.the official number and name C.the port of registry and name D.the port of registry and official number
单项选择题 Every state, whether coastal or not,（）to sail ships under its flag on the high seas.
单项选择题 How many（）are there altogether?
单项选择题 I can hardly understand（）you said.
