单项选择题
A.压力B.弹性C.应力D.铁锈
A.30minB.40minC.50minD.60min
A.输油管线-发油泵-集油管-卸车鹤管B.卸车鹤管-输油管线-发油泵-集油管C.输油管线-卸车鹤管-发油泵-集油管D.输油管线-卸车鹤管-集油管-发油泵