在电力系统正常状况下，35kV及以上电压供电的电压正、负偏差的绝对值之和不超过额定值

下列各组气体遇到明火可能发生爆炸的是[ ]

A．CO、H₂

B．CH₄、O₂

C．N₂、O₂

D．H₂、CO₂

能量饲料

在LFP-901A保护装置中为什么引入工频变化量阻抗元件ΔZ？

George Ernest Morrison, an Australian, traveled the "five-foot roads," or foot paths, from Shanghai to Rangoon in 1894, ______ China before it was engulfed in a century of revolution, war and political tumult.

A．witness

B．witnessed

C．witnessing

D．to witness

确诊消化性溃疡首选的检查方法是

A．B超

B．X线

C．幽门螺旋杆菌检测

D．胃镜

E．胃液分析