The correct answer is (a). The Pala dynasty was a Hindu dynasty that ruled over Bengal and Bihar in eastern India from the 8th to the 12th centuries. The Pratihara dynasty was a Hindu dynasty that ruled over Malwa and Gujarat in northwestern India from the 7th to the 10th centuries. The Rashtrakuta dynasty was a Hindu dynasty that ruled over Deccan in southern India from the 8th to the 10th centuries. The Chola dynasty was a Hindu dynasty that ruled over Tamil Nadu in southern India from the 9th to the 13th centuries.
The tripartite struggle in South India was a conflict between the Chola, Pandya, and Chera dynasties that lasted from the 9th to the 13th centuries. The Chola dynasty emerged victorious from the conflict and became the dominant power in South India.
The Pala dynasty was not a part of the tripartite struggle in South India because it was located in eastern India, far from the Deccan region where the conflict took place. The Pala dynasty was also a Buddhist dynasty, while the Chola, Pandya, and Chera dynasties were Hindu dynasties.