Why can leaves be small or thorny in dry regions?

Correct answer: They help reduce transpiration

The direct answer is option D: they help reduce transpiration. Transpiration is the loss of water vapour from a plant, mainly through tiny openings in leaves called stomata. In dry regions, water is scarce, so plants develop adaptations that reduce water loss. A smaller leaf has less surface area, and a thorn is a modified leaf with very little exposed surface. Step by step: less leaf surface means fewer opportunities for evaporation; reduced evaporation helps the plant retain water; retaining water improves survival in dry conditions. Option A is wrong because these structures do not aim to lose more water. Option B is wrong because leaves do not mainly stop rainfall. Option C is wrong because they do not remove soil. Option D is correct because small leaves and thorns reduce transpiration, often along with waxy surfaces or deep roots. Memory cue: “Dry climate, tiny leaves, less water loss.”