变压器系_________、________跳闸,在未查明原因和消除故障之前,不得送电
参考答案:瓦斯,差动保护动作
The number of the students in our school ________ about 3000 and ______ them study hard.
A.is, a large amount of
B.are, a number of
C.are, large amount of
D.is, a large number of
三因治宜是指:()。
A、因地
B、因人
C、因时
D、因病