The correct answer is "The British wanted Indian soldiers to use rifle cartridges that were greased with animal fat."
The reason why this caused the Sepoy Rebellion was because many of the Indian soldiers were Hindus. In the Hindu religion, the cow is a sacred animal. Hindus are not able to eat, touch, or kill cows.
Even though this was the case, the British wanted the Indian soldiers to grease their rifle cartridges with a mixture of beef and pork fat. This went against many Sepoys religious beliefs. Despite this, the British did not change their ammunition methods, which helped to spark this rebellion.
