单项选择题
Fire alarm system thermostats are actuated by（）.
A.smoke sensors B.the difference in thermal expansion of two dissimilar metals C.pressure loss due to air being heated D.an electric eye which actuates when smoke interferes with the beam
单项选择题 Except in rare cases，it is impossible to extinguish a shipboard fire by（）.
单项选择题 Control valves of a CO2 system may be located within the protected space when（）.
单项选择题 CO2 cylinders，which protect the small space in which they are stored must（）.
