Jenny always the bus?[ ]
A. Does, take
B. Do, takes
C. Do, take
D. Does, takes
答案:A
电梯安装之前,所有层门预留孔必须设有高度不小于()的安全保护围封,并应保证有足够的强度。
A.800mm
B.1000mm
C.1100mm
D.1200mm
A.电源电压;
B.灯泡两端的电压;
C.灯丝电阻;
D.灯泡的额定功率