单项选择题
A combination or all-purpose nozzle produces（）.
A.low-velocity fog only B.a solid stream only C.a solid stream and foam D.a solid stream and fog
单项选择题 A CO2 portable extinguisher is annually checked by（）.
单项选择题 A CO2 extinguisher on a ship which has lost 10% of its charge must be（）.
单项选择题 A branch line valve of a fire extinguishing system on a ship must be marked with the（）.
