Match the pressures with the event they cause.
| Column I | Column II |
|---|---|
| (a) Intra-pulmonary pressure is less than atmospheric pressure | (i) Expiration |
| (b) Intra-pulmonary pressure is higher than atmospheric pressure | (ii) Inspiration |
| (c) Negative pressure in the lungs with respect to atmosphere | (iii) Inspiration |
| (d) Positive pressure in the lungs with respect to atmosphere | (iv) Expiration |