What features do plants use to regulate and conserve water?
a. guard cells
b. stomata
c. cuticle
d. all of the above

d. All of above

Explanation:

Cuticle refers to the waxy covering that is present outer to the epidermis of aerial parts of the plants. It is made of water repellent substance cutin which in turn does not allow the loss of water from plants.  

The minute pores mainly present in the epidermis of leaves of plants are called stomata. The stomatal pores are surrounded by chloroplast containing cells called guard cells. Change in the shape of guard cells regulates the opening and closing of stomata and thereby regulates the loss of water from plants by the process of transpiration.

The plants found in the habitats with water scarcity have thick cuticle layers over their aerial parts and keep the stomata close during hot day time to reduce water loss.