The correct answer is A) low crop prices.
Low crop prices was a factor that contributed to the formation of the Farmers' Alliance.
The Farmers' Alliance was formed by many farmers groups after the depression of 1870. Among the many organizations that were part of the movement were the Industrial Union, the National Farmer's Alliance, and the Colored Farmers National Alliance. The movement aimed to fight for the rights of the farmers, to raise the prices of the crops, and supported the intervention of the government to regulate transportation.