单项选择题
The shear rams of a ship blowout preventer stack are used in emergency well control to（）.
A.close and seal around the drill pipe B.close and seal around casing C.cut off pipe inside the preventer stack D.close and seal around drill collars
单项选择题 The rated operating time of a self-contained breathing device may be reduced in actual use because of（）.
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（）.
