The cells in regions B and C in Fig. 3.1 have a large surface area. Explain why this is necessary for the functioning of the leaf cells.

(cell surfaces are sites of) gas exchange ; movement of gases by diffusion ; ref. to efficient / faster / AW, gas exchange / diffusion / photosynthesis ; carbon dioxide is, raw material / needed, for photosynthesis ; absorption of carbon dioxide (when light available) ; loss of oxygen (when light available) / absorption of oxygen ; oxygen is required for (aerobic) respiration ; more evaporation ; idea of maximising light absorption ;