The bikehe went to school was stolen last week,which made him feel sad.

He borrowed a book the other day ， the authoris a worker.

Mrs Zhang often tells us that spring is the timepeople go sight seeing.

Believe it or not,I dont like the wayhe spoke to me.

As is known to us all,the agechildren can go to school is seven.

相向掘进的巷道相距米时，必须停止一个头掘进。

瓦斯爆炸的三个条件是：一是浓度的瓦斯;二是温度为以上引爆火源;三是空气中氧浓度。

煤矿井下电气事故主要有事故、事故、事故和事故。

矿井通风系统担负着向井下输送足量供人呼吸，排放，创造井下良好作业环境的重要任务。

炮采工作面容易出现的问题主要有：、和。