The correct answer is C) the materials used to make rifles.
The incident that started the Sepoy Rebellion was related to a rumor about the materials used to make rifles.
In 1857, people from Indian started a rebellion against the British. This violent uprising was also known as the Indian Rebellion or the Indian Mutiny. Historians consider that this rebellion was the first violent expression of the demands of the people to be independent. And yes, a new kind of rifle cartridge caused problems because the rumor said that the grease used to make the cartridges were from pigs and cows, considered sacred animals in India.
The other options of the question were A) the working conditions at trading posts. B) the working conditions at textile factories. D) the materials used to sew soldier's uniforms.