单项选择题
A.to keep the boats covered at all times
B.not to leave steel or iron tools lying in or near these boats
C.to keep an electric charge on the hull at all times
D.to rinse these boats regularly with salt water
单项选择题 All inflatable liferafts have（）.
单项选择题 After conducting an abandonment drill，the Master or person in charge of a ship shall log（）.
单项选择题 According to the Code of Federal Regulations，on vessels other than river ferryboats and river vessels，how are periodic lifeboat weight tests required to be conducted?（）