Assertion (A): Capillaries have walls that are just one cell thick.
Reason (R): Exchange of material between the blood and surrounding cells takes place across the capillaries.
- Capillaries are vessels that are one cell thick and are responsible for exchange of nutrients and waste between the blood and cells.
- This exchange of material takes place through diffusion and is only possible because of their low thickness.
The correct answer is A .
Both A and R are true.