大家都搜：
氧气两次
1、exchanges oxygen───交换氧气
2、twice wiki───两次wiki
3、thinking twice───再三考虑；重新考虑
4、oxygen mask───n.（供人吸氧时用的）氧气面罩；n.氧气面罩
5、oxygen───n.[化学]氧气，[化学]氧
6、twice───adv.两次；两倍
7、cannula oxygen───套管氧气
8、supplemental oxygen───[医]补充供氧，辅助供氧
9、oxygen deficit───缺氧
1、The Dutch mountaineer, who already scaled Everest without supplementary oxygen and attempted K2 twice before, also has a number of spectacular polar expeditions to his credit.───这个荷兰登山者，已经无氧攀登了珠峰，在之前又尝试两次攀登K2，拥有非常丰富的极地探险经验。
2、(It is recommended that you use) Use Dr. Oxygen twice a day for daily healthful living!───（因此建议您使用）使用氧气博士每天两次每天健康生活！
3、the same amount of carbon, there is twice as much oxygen as in carbon monoxide.───同一份量的碳，所需要的氧的分量却是一氧化碳的二倍。
4、Sulfur is twice as heavy as oxygen.───硫是氧的两倍那么重。