Final answer:
The primary reason for the war against the Khanate of Kazan was territorial disputes. The Mongols sought to expand their territory and establish dominance over the Kazan region.
Step-by-step explanation:
The primary reason for the war against the Khanate of Kazan was A) Territorial disputes. The Mongols sought to expand their territory and control over the Kazan region, which was strategically important for them. They wanted to establish their dominance and gain access to valuable resources and trade routes.