Option c is the correct answer. The Tripartite Struggle for Kannauj was a prolonged conflict lasting over two centuries among the Pala Empire, the Gurjara-Pratihara Empire, and the Rashtrakuta Empire. The strife centered around gaining control over the strategic and economically prosperous Kannauj region. This area's strategic location facilitated trade routes and military movements, while its economic prosperity stemmed from its fertile lands and commercial activities. Eventually, the Gurjara-Pratiharas prevailed, and Nagabhata II established Kannauj as their capital.