Introduction:
The Kaveri River, also known as the Cauvery River, is one of the major rivers in India. It flows through the southern states of Karnataka, Kerala, and Tamil Nadu. Let's explore why the correct answer is option 'D' - Karnataka, Kerala, and Tamil Nadu.

Karnataka:
- The Kaveri River originates in the Brahmagiri Hills of Kodagu district in the state of Karnataka.
- It flows through various districts of Karnataka, including Mysore, Mandya, and Ramanagara.
- The river plays a significant role in Karnataka's agriculture, serving as a source of irrigation for crops like rice, sugarcane, and coconut.

Kerala:
- After flowing through Karnataka, the Kaveri River enters the state of Kerala.
- It travels through the Wayanad district, providing water for irrigation and drinking purposes.
- The Kabini River, a tributary of the Kaveri, also flows through Kerala, further adding to the water resources of the state.

Tamil Nadu:
- The Kaveri River then enters the state of Tamil Nadu, where it plays a vital role in the state's economy and culture.
- It flows through various districts, including Dharmapuri, Erode, and Trichy.
- The river is of great importance to Tamil Nadu's agriculture, particularly in the Cauvery Delta region, known as the "Rice Bowl of Tamil Nadu."
- The Cauvery Delta is a fertile agricultural region where paddy fields thrive due to the river's water supply.
- The river also holds religious significance, with numerous temples and shrines located along its banks.

Conclusion:
In conclusion, the correct option is 'D' - Karnataka, Kerala, and Tamil Nadu. The Kaveri River originates in Karnataka, flows through Kerala, and plays a crucial role in Tamil Nadu's agriculture and culture. Understanding the path and significance of this river helps us appreciate its importance to the regions it traverses.