当氧压机的润滑油进入汽缸后,氧气压缩后温度升高,使油脂挥发后与氧气混合,将导致()
A、氧气纯度下降
B、发生顶缸事故
C、影响闪速炉用氧
D、机组燃烧爆炸
参考答案:D
—Another cup of coffee? That’s your third since lunch.
—Yeah, well, I ____ all night preparing for my history exam. I can hardly keep my eyes open.
A.stayed up
B.have stayed up
C.have been staying up
D.will stay up
田间持水率