In order to discharge a C02 portable fire extinguisher , the operator must first().
A. invert the CO extinguisher
B. squeeze the two trigger handles together
C. remove the locking pin
D. open the discharge valve
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IDD和DDD分别指()
A. 国际长途直拨和国内长途直拨
B. 店内直拨和店外直拨
C. 国内长途直拨和国际长途直拨
D. 市内直拨和长途直拨