儿童游戏以游戏的教育作用为依据分为()、()、()、()、()、()、()。
As an extinguishing agent,foam().
A. conducts electricity
B. should be directed at the base of the fire
C. is most effective on burning gases which are flowing
D. extinguishes by cooling oil fires below ignition temperature
可使用R12也可使用R22的氟压缩机,内充R12时,其运行参数有何变化?(与充R22时相比)
举止主要指()
A. 坐姿
B. 站姿
C. 走姿
D. 容姿
E. 手势