1. However, it is too expensive to go by air.
    然而, 坐飞机太贵了.

2. Humidity means the amount of moisture in the air.
    湿度指空气中水汽的含量。

3. He ripped the letter open with a knife.
    他用刀子一下子把信裁开了。

4. His mouth was half open with dribbling saliva.
    他的嘴半张着, 淌着口水。

5. His answer was to lift the vessel out of the water by making it ride on a cushion of air, no more than one or two feet thick. This is done by a great number of ring-shaped air jets on the bottom of the craft.
    他的解决办法是把船体提离水面，让船在一个气垫上行驶，气垫只有一两英尺厚。船底装上大量环状喷气嘴以实现这一目的。

6. He dresses, washes, and goes out to do exercises in the fresh morning air.
    他穿好衣、洗完脸，就走到室外，在清爽的晨风中做早操，

7. He came home the same way, the front door flying open, his cap on the floor, and the voice, suddenly rough, shouting, "Isn't anybody here?"
    他回家时还是那副粗鲁样：撞开前门，把帽子往地板上一扔，突然粗着嗓门喊道："家里有人吗？"

8. However, the collective smoke from thousands of factories, over the past two centuries, has caused enormous increases in air pollution levels worldwide.
    但是，在过去的两个世纪中，从千万家工厂排放出的烟尘已大大加剧了全球大气的污染度。

9. Human population growth is creating food shortages, problems of air quality, and changes in weather patterns.
    人口的增长带来了粮食短缺、空气质量降低、天气状况变化等问题。

10. Does that window open inwards or outwards?
    那个窗户是向里开，还是向外开？