题目内容
肺内压的存在使得肺被牵拉而始终处于扩张状态,避免肺出现塌陷。
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气体交换只在肺泡周围进行。
气体交换是用一个肺泡中的氧气与一个肺泡毛细血管的二氧化碳进行交换。
肺泡进行气体交换的原理是肺泡与肺泡中的气体(氧气和二氧化碳)存在浓度差。
1. Mary found that ______________ was always the best policy when she got involved in arguments with her husband.2. If you are not _________ with your present job, you should find out what you need to do to qualify for a better one.3. I’d like very much to buy the camera. ___________, I haven’t got enough money on me.4. No one else can tell you what is best for you because every ____________ is different.5. The operation was something of a _________, but without it it was just a matter of time before the cancer killed her.6. The policeman ________ his car round and sped after the fleeing criminals.7. Its charm and mild climate have made San Francisco an _____________ city for both business and residence.8. If you come to my office about twelve, we can have lunch together and meet the manager ____________.9. Egypt has a long cultural __________ which is deeply rooted in the history of the country.10. This stamp is __________: all others like it have been lost or destroyed.11. The computer science professor promised to help his students if new difficulties _________ in their research.12. The new office boy seemed smart and _________ when he reported for work.
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