空气预热器的投用后，可以减少（）的消耗。
A、油品
B、氢气
C、人力
D、燃料气
参考答案：D
— Can you keep an eye on my bag? I just want to use the bathroom.
— _____ It'll be safe with me.[ ]
A. Sure, why not?
B. Take it easy
C. Go ahead.
D. Not at all.
保护装置工频试验电压500V的回路有哪些？
