物料粉碎的难易程度，称作（）。
A.破碎比
B.硬度
C.易碎性
参考答案：C
ZFSB4000/17/28型低位放顶煤支架的工作阻力是（）KN.
A、4400
B、4200
C、4000
-Where is Mike? He asked me to go out for a walk this evening
-Maybe he ________ TV in the living room now.
A. is watching
B. will watch
C. watched
D. watches
