Question

why should breadth through our nose ratter than breathing through our mouths

Answer 1

because while breathing through nose your nose will have mucus and hair which is somewhat sticky type..so the air which is inhailed will have some dirt particles sooo thoses things will  get caught by the mucus and come out in the form of waste from our nose

where as mouth doesnt have any such protective elements

Answer 2

bcz inside our nostrils their are several tiny hairs which traps the dust and germs of air instead if we will breath with mouth the dust will reach our lungs.