理论分选密度1.5,密度级1.4~1.6时产率为25.8%,该煤属于()
A、难选煤
B、较难选煤
C、易选
参考答案:B
The performance supposed to be popular _____ to be a great disappointment after it was over.
A.turned up
B.turned down
C.turned out
D.turned over
以下()等负载,可近似看成纯电阻性负载。
A.白炽灯
B.电阻炉
C.变阻器
D.线圈