由于种种原因，输气管道内的天然气中含有数量不等的硫化氢、二氧化碳、凝析水，但它们对管道的内壁不起腐蚀作用。
参考答案：错
When something is on fire. People throw sand (沙子) on it to put out the fire. The main use of the sand is to
________. [ ]
A. protect the thing on fire.
B. add weight to the thing on fire.
C. keep the air away from the thing on fire.
D. lower the temperature of the thing on fire.
临终患者心理状态的发展阶段不包括
A．忧郁阶段 B．否认阶段C．麻木阶段 D．愤怒阶段E．接受阶段
