在采掘工作面回风巷风流中CO2浓度超过1.5时必须停止工作，撤出人员，制订措施，进行处理。
参考答案：对
He must have passed this way, _____here are his footprints.
A．since
B．because of
C．now that
D．for
肺结核病的全身中毒症状有()
A．盗汗
B．咯血
C．低热
D．乏力
E．咳嗽
