Correct Answer - c
Large number of tiny pores called stomata are present on the surface of the leaves of plants. The gaseous exvhange as well as transpiration takes place through these pores. The opening and closing of the pore is a function of the guard cells.
The guard cells swell when water flows into them,causing the stomatal pores to open.
Similarly the pore closes if the guard cells shrink or losses water in them.
