A “fifteen-pound” CO2 extinguisher is so c
题型：单项选择题
问题：
A “fifteen-pound” CO2 extinguisher is so called because（）.
A.there are fifteen pounds of CO2 in the container
B.the container，when full，weighs fifteen pounds
C.the pressure at the discharge nozzle is l5 psi
D.the empty container weighs fifteen pounds