采用钻屑法进行预测预报时,每个测试孔(),测定每米钻粉量,临界指标待定。预测有冲击地压,必须停止工作,采取卸压措施,待效果检验解除冲击危险时方可恢复作业。
参考答案:8~10m
若a<0,b<0,则a-(-b)一定是 (填负数,0或正数)
We don’t permit _____in the classroom; that is to say, students aren’t permitted _____in the classroom.[ ]
A. to smoke; to smoke
B. smoking; smoking
C. smoking; to smoke
D. to smoke; smoking