如何判断变压器是否正常？
参考答案：
将220v电接入变压器一端，用万用表量另一端电压是否稳定正常。
Apples are usually sold by ______weight, and eggs are sometimes sold by ______ dozen.
A．the; the
B．不填; a
C．不填; the
D．the; a
钻遇高压油气层都有哪些显示？
