单项选择题
Two individuals authorized to serve as a lifeboatman must be assigned to any lifeboat that has a capacity of more than（）.
A.10 persons B.20 persons C.30 persons D.40 persons
单项选择题 The water pockets located on the underside of inflatable liferafts（）.
单项选择题 The signal given to commence lowering the lifeboats is（）.
单项选择题 The order to enter the lifeboats will be given from the（）.
