Concept:The opening and closing of stomata depends on the change in turgor pressure of guard cells due to water movement.
Explanation:Guard cells surround each stomatal pore.
When they absorb water, they become turgid and swell.
This swelling bends the guard cells outward, opening the stomatal pore.
When guard cells lose water, they become flaccid and shrink.
This makes the pore close.
Therefore, the whole mechanism is based on turgidity and flaccidity of guard cells.
Answer:B. turgidity and flaccidity