单项选择题
A.keep the propeller from being fouled
B.increase propeller speed
C.help calm the waves in the vicinity of the craft
D.increase the holding power of the sea anchor
单项选择题 Reid vapor pressure is（）.
单项选择题 Regulations require that tankers handling grade B liquids shall have their cargo pumps separated from all sources of vapor ignition by（）.
单项选择题 Regulations require that tank vessels handling grade B liquids shall have their cargo pumps separated from all sources of vapor ignition by（）.