单项选择题
A pilot vessel may continue to sound an identity signal if she is （）.
A.aground B.at anchor C.not under command D.being towed
单项选择题 A pilot chart does NOT contain information about （）.
单项选择题 A petroleum liquid has a flash point of 85°F. This is a grade （）.
单项选择题 A negative metacentric height （）.
