Correct option:(4)(a) and (b)
Solution:
During inspiration:
- Contraction of diaphragm takes place and it moves down.
- Downward movement of the diaphragm causes less intrapulmonary pressure than the atmosphere.
- External intercostal muscles also contract and cause the ribcage to be able to move outward.
- This increases the pulmonary space and decreases the pulmonary pressure.
- Both these movements cause inspiration.