单项选择题
A hygrometer is a device used for determining（）.
A.the absolute temperature B.atmospheric pressure C.wind velocity D.relative humidity
单项选择题 A large oil fire on the deck of a ship can be fought most effectively with（）.
单项选择题 A life line must be conncted to the life raft（）.
单项选择题 A life raft which has inflated bottom-up on the water（）.
