Which river forms the border between Telangana and Andhra Pradesh?

Option A (“Godavari”) is incorrect because it does not match the river basin, lake type, location, tributary relationship, project or hydrological feature specified in the question. Option C (“Tungabhadra”) is incorrect because it does not match the river basin, lake type, location, tributary relationship, project or hydrological feature specified in the question. Option D (“Pranahita”) is incorrect because it does not match the river basin, lake type, location, tributary relationship, project or hydrological feature specified in the question. The key concept is to match the water body with its basin, type, location and defining feature. Therefore the correct option, index and explanation consistently identify Krishna. The Krishna River forms a natural boundary between Telangana and Andhra Pradesh for a significant portion. The river originates from Mahabaleshwar in Maharashtra and flows through Karnataka before entering Telangana and Andhra Pradesh, finally draining into the Bay of Bengal.