单项选择题
A rigid lifesaving device only designed for survivors to hold on to while in the water is a（）.
A.liferaft B.life float C.life preserver D.buoyant apparatus
单项选择题 A rigid lifesaving device designed to support survivors in the water is a（）.
单项选择题 A liferaft which has inflated bottom-up on the water（）.
单项选择题 A life line must be connected to the liferaft（）.
