轻瓦斯动作后收集到的气体为无色无味不易燃的气体时,则可判断变压器内部()。
A.相间短路;
B.铁心片间短路;
C.单相接地;
D.无故障。
参考答案:D
管道设备的换气工作可以在夜间进行。
20.It was four o'clock in the afternoon_____he and his grandpa reached the museum in Guanghan, _____an official warmly received them.
A.that; where
B.when; that
C.when; where
D.that; when