What is the difference between mechanical and chemical weathering?

Mechanical weathering breaks rocks into smaller pieces without changing their composition and chemical weathering breaks down rocks by forming new minerals that are stable at the Earth's surface.

air enters through the nose, moves through the nasal cavity, the pharynx, the larynx, enters the trachea, moves through the bronchi andbronchioles till the alveoli.

i think its both a and b