The correct answer is option 3 - Tamil Nadu and Karnataka. The Cauvery water sharing dispute is a long-standing issue between these two states in India. The conflict revolves around the equitable allocation of water from the Cauvery River, which flows through both states. Tamil Nadu claims historical usage rights and argues that it requires a certain amount of water for its agricultural needs. Karnataka, on the other hand, argues that it needs the water for its own agricultural and domestic purposes. Over the years, there have been numerous legal battles and negotiations between the two states to resolve this contentious issue. The dispute has often led to protests, unrest, and even violence in both regions.