Final answer:
Stomata allow CO₂ to enter the plant for photosynthesis and can close to prevent water loss. Guard cells regulate stomatal opening and closing, balancing gas exchange and water conservation. The correct answer is b) Allows, Prevents.
Step-by-step explanation:
Stomata allow CO₂ to diffuse into the plant for photosynthesis and can close to prevent excess water loss through transpiration. The guard cells regulate the opening and closing of stomata in response to various environmental cues.
When stomata are open, they allow for the exchange of gases; oxygen and carbon dioxide can diffuse in and out, which is necessary for photosynthesis. However, this also increases the rate of water vapor loss.
To balance the need for carbon dioxide intake with the risk of excessive water loss, plants can close their stomata to conserve water, especially in conditions of water scarcity or high temperature.
Therefore, the correct answer to the student's question is: b) Allows, Prevents. Stomata allow CO₂ to enter the plant, which is necessary for photosynthesis, and the guard cells can close the stomata to prevent water loss, ensuring a balance between gas exchange and water conservation.