采用充填采矿法回采矿石时,要用充填材料充填回采空间,实现采场地压控制。充填体的作用是()。
A.避免矿石贫化
B.提高矿石运输效率
C.减少围岩暴露面积
D.降低地表下沉
参考答案:D
个人的职业道德境界只决定于个人的主观努力、自我修养。( )
Most of us know we should cut down on fat, but knowing such things isn't much help when it ________ shopping and eating. [ ]
A. refers to
B. speaks of
C. focuses on
D. comes to