1度电可供额定功率为25瓦的灯泡正常发光______小时.
功率:P=25W=0.025kW.
时间:t=WP=1kW•h0.025kW=40h.
故答案为:40.
______ at the door before entering please.
A.Knocked
B.Knock
C.Knocking
D.To knock
摄像机的报警输出口可以接入红外双鉴报警器。()