Khadins, Bundhis, Ahars, and Kattas are ancient structures that are examples for (c) water harvesting.
Explanation: These terms refer to traditional methods of capturing and storing rainwater in arid and semi-arid regions of India, making them structures primarily designed for water conservation.
Key points about the options:
(a) grain storage: While some structures might be used for grain storage, Khadins, Bundhis, Ahars, and Kattas are specifically designed for water collection.
(b) wood storage: There’s no direct connection between these structures and wood storage.
(d) soil conservation: Although water harvesting can contribute to soil conservation by reducing erosion, these structures are primarily built for water collection.