The correct answer is small leaves, also called xerophytic adaptation.
Rajasthan is largely an arid and semi arid region with very low rainfall and high temperatures, especially in the Thar Desert area. Plants growing here, such as Khejri, Babul and various cacti, have adapted to survive with limited water.
One key adaptation is small or reduced leaf size. A smaller leaf surface area means less water is lost through transpiration, which helps the plant conserve moisture in a dry climate. This feature is common in what botanists call xerophytes, or plants suited to dry environments.