Plants make their own food through the process of photosynthesis. To do this, they need energy from the Sun, carbon dioxide from
the air, and water and other nutrients from their roots.
Carbon dioxide enters the plant through tiny openings on the underside of leaves known as stomata. However, whenever the plant
opens its stomata to let carbon dioxide in, it also releases water vapor into the atmosphere. This latter process is known as
transpiration.
Under which of the following environmental conditions would you expect the stomata to be closed more often than they are open?
A. on a hot, dry day
B. on a cool, cloudy day
c. on a wet, rainy day
D. on a warm, windy day