Which is the proper method of determining whether a portable CO2 fire extinguisher needs recharging?（）
- ACheck the tag to see when the extinguisher was last charged
- BRelease a small amount of CO2; if the CO2 discharges，the extinguisher is acceptable
- CWeigh the extinguisher and compare the weight against that stamped on the valve
- DRecharge the extinguisher at least once each year