Geographic locations of cities:
- Kannauj: Northernmost city, in Uttar Pradesh.
- Pataliputra: Ancient name for Patna, in Bihar.
- Rajahmundry: Southern India, in Andhra Pradesh.
- Karur: Southernmost city, in Tamil Nadu.
North to South Arrangement:
The sequence from north to south is Kannauj (a) → Pataliputra (c) → Rajahmundry (d) → Karur (b).
Final Answer: (2)