Who were the primary competing kingdoms involved in the historic Tripartite Struggle for control over Kannauj in northern India from the $8^{\text{th}}$ to the $10^{\text{th}}$ century?

1. A
   The Palas, Cholas, and Pallavas
2. B
   The Palas, Pratiharas, and Rashtrakutas
3. C
   The Cholas, Pratiharas, and Rashtrakutas
4. D
   The Palas, Cholas, and Rashtrakutas