1. Plants absorb oxygen.
    植物吸收氧气.

2. Mars is too dry and poor in oxygen, Venus far too
    火星上面过于干燥，并且缺乏氧气。金星温度太高了.

3. Mars is too dry and poor in oxygen,
    火星太干燥又缺氧，

4. It is bacteria that have generated the oxygen we breathe on earth.
    正是细菌生产出我们在地球上呼吸的氧气。

5. Fatigue and poor performance may begin to appear in the second stage of deficiency, when not enough iron is present to form the molecules of blood protein that transport oxygen to the working muscles.
    到了缺铁的第二阶段，就会出现疲倦和力不从心，此时体内已没有足够的铁来形成血蛋白分子，将氧输至运动着的肌肉。