Compare three components of inhaled air with that of exhaled air

These are oxygen,Carbon dioxide and water vapour.

Explanation:

The inhaled air has 21% oxygen,0.04% C02,and  less water vapour.

Exhaled air contains more C02-4%, 16%-O2 and more water vapour about 6.3%.

The higher 02 of the inhaled air  is needed for the supply of lung tissues for the respiration of the cells.Therefore higher volumes is needed to meet up with the larger demands by the cells. The oxygen is needed for cellular respiration which leads to production of more C02 and water vapour in exhaled air.

Therefore, their elevated levels(C02-4%) in exhaled air is due to this mechanisms.This made the exhaled air to be saturated with water vapour

They are the wastes products of cellular respiration in animals. (however the volume of the oxygen in the exhaled air drops to 16% from 21%)because it is used as fuel to burn glucose).

Th volume of C02 in the inhaled air is low because this is not needed for cellular respiration,this it volume of (0.4) compared to the inhaled air.

Generally, the lower levels of C02 is needed so that the diffusion gradients for the  movement of C02 out of the lungs is achieved . Hence waste gasses are  not retained in the body. Likewise the higher  volume of oxygen (21%) is needed for the inwards diffusion  gradient of oxygen into the blood  for ventilation of the lungs,and aeration of cells.

More water vapour are produced in the cells,therefore they must be diffused out of the cells in the blood.Hence higher percentage in the exhaled  compare to the inhaled air

a "theory" a suggestion that is not 100 % accurate, or a figure. some people say its a theory because they of all the passed theory's about one subject. it depends sometimes theory might be accurate and sometimes they are.