Select the correct events that occur during inspiration.

(a) Contraction of diaphragm

(b) Contraction of external inter-costal muscles

(c) Pulmonary volume decreases

(d) Intra pulmonary pressure increases

1. (c) and (d)

2. (a), (b) and (d)

3. only (d)

4. (a) and (b) 

Select the correct statement: