下列做法中，符合安全用电常识的是[ ]
A．湿手触碰开关
B．用铜丝代替保险丝
C．雷雨天在大树下避雨
D．发现有人触电立即切断电源
答案：D
He was driving a lorry load of bananas ____he came off the road at a bend and fell into the valley.
A．since
B．until
C．when
D．while
发电机的调相运行，是指发电机不发有功功率，主要用来向电网输送感性无功功率。
