单项选择题
The rated operating time of a self-contained breathing device may be reduced in actual use because of（）.
A.pressure differences in the atmosphere B.the length of the hose attached to the facepiece C.the physical exertion of the person wearing the device D.spaces containing poisonous vapors
单项选择题 The radiotelephone urgency signal is（）.
单项选择题 The Muster List (“Station Bill”) shows each person’s lifeboat station，duties during abandonment，basic instructions，and（）.
单项选择题 The Master shall insure that the Emergency Position Indicating Radio beacon (EPIRB) is（）.
