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1·If the theory was correct, breathing air with extra carbon dioxide should have triggered yawning, while breathing pure oxygen should have suppressed yawning.

如果这个理论是正确的，那么吸入含有额外二氧化碳的空气应该会引起打哈欠，而吸入纯氧应该可以抑制打哈欠。

2·Volunteers were told to think about yawning while they breathed either normal air, pure oxygen, or an air mixture with an above-normal level of carbon dioxide.

当志愿者在正常的空气中、纯氧的环境下，或者混有超过正常的二氧化碳含量的空气中呼吸时，他们被要求要想着打哈欠。

3·Volunteers were told to think about yawning, while they breathed either normal air, pure oxygen, or an air mixture with an above-normal level of carbon dioxide.

当志愿者在正常的空气中、纯氧的环境下，或者混有超过正常的二氧化碳含量的空气中呼吸时，他们被要求要想着打哈欠。

4·True, but not pure oxygen.

没错，但是那不是纯氧。

5·Pure oxygen is given to patients in certain circumstances.

某些情况下给病人吸纯氧。

6·Pure oxygen must be given patients in certain circumstances.

在某些情况下必须给病人吸纯氧。

7·In the new system, the coal is burned in pure oxygen instead of air.

在新系统中，煤炭在纯氧而不是空气中燃烧。

8·This item has been cleaned for a special service such as pure oxygen.

该产品已经清洗可用于如纯氧的特殊场合。

9·Nitrogen is removed from the air, enabling the fuel to burn in pure oxygen.

氮气从空气中被去除，使得燃料能够在纯氧中燃烧。

10·Pure oxygen must be given to patients in these kinds of circumstances.

在这些情况下，纯氧必须给病人。