钢包吹氩的目的主要是让夹杂物上浮，对钢水温度和成分没作用。
参考答案：错
—Was it there _______ you were away to answer the phone? —There is no doubt about it.
A．that
B．which
C．while
D．where
矿灯管理人员应每班统计矿灯出勤率，并上报调度室。
