单项选择题
Combustible gas indicators measure the presence of combustible gas as a percentage of the（）.
A.flash point B.upper explosive limit C.lower explosive limit D.fire point
单项选择题 CO2 extinguishes a fire by（）.
单项选择题 Cargo transfer operations on a tanker need NOT be stopped when（）.
单项选择题 Blocking open or removing fire dampers can cause（）.
