Question

How much percentage of oxygen has expired?
A. 7%
B. 25%
C. 15%
D. 20%

Answer 1

Hint: Oxygen is a chemical element. It is known to be a highly reactive non-metal. It is used by living organisms for respiration. Oxygen is produced by plants during photosynthesis.

Complete answer:
Oxygen is a highly reactive non-metal which is used by living organisms for respiration and metabolic activities. Plants play a crucial role in generation of oxygen. Earth’s atmosphere is composed of 21% oxygen, 78% nitrogen and 1% of other gases such as carbon, neon, hydrogen.
When oxygen is combined with hydrogen, carbohydrates are formed that provides energy to our body. It is also important for our immune system as it kills bacteria, virus. Oxygen is not only important for respiration but also for cells and cell organelles to work. Animals and human beings take up oxygen and give off carbon dioxide.
Oxygen is not only important for living things but for other things such as fuel burning, and other combustion activities.
Inhaled air has 79% nitrogen, 21% oxygen and some amounts of other gases whereas exhaled air has 5% carbon dioxide, 79% nitrogen and 15% oxygen.

Hence, the correct answer to this question is option ‘C’- 15%.

Note: If earth is deprived of oxygen even for five seconds, life on earth will become very dangerous as the ozone layer is made up of oxygen. Ozone layer protects the earth from ultraviolet radiations coming from the sun. Thus, no oxygen is equivalent to no ozone layer and hence no life.