The correct answer is A. xerophytes.
Xerophytes are plants that have adapted to living in dry environments. They have a number of features that help them to conserve water, such as thick, waxy leaves, deep roots, and a small surface area.
Mesophytes are plants that grow in moderate climates with evenly distributed rainfall. They have neither the specialized features of xerophytes nor the specialized features of hydrophytes.
Lithophytes are plants that grow on rocks. They have a number of features that help them to adhere to the rock surface and to withstand the harsh conditions of the rock environment, such as a thick, corky outer layer and a shallow root system.
Hydrophytes are plants that grow in water. They have a number of features that help them to survive in the aquatic environment, such as aerenchyma (air-filled tissue) that helps them to float, and hydrophyllic leaves (leaves that are adapted to absorb water and nutrients from the water).