(i) How does the

(i) Oxygen enters the body in the mouth and nose, passes through the larynx and the trachea.

As shown in the diagram given below:

(ii) Nose - The nose is the primary organ of smell and also functions as part of the body's respiratory system.

Mouth – Mostly the breathing is done through nose i.e. nasal cavity. But, it can be done through oral cavity as well.