单项选择题
Operation of the valve control release on a fixed CO2 system must immediately（）.
A.release CO2 to the protected space B.secure all mechanical ventilation in the protected space C.sound the rig's general alarm signal for a fire D.sound an alarm in the ballast control room
单项选择题 One of the limitations of foam as an extinguishing agent is that foam（）.
单项选择题 One disadvantage of using regular dry chemical (sodium bicarbonate) in firefighting is that（）.
单项选择题 One advantage of the all-purpose nozzle is that it（）.
