Answer:
The correct answer would be option B, Low crop prices and lack of government aid.
Step-by-step explanation:
Populist was basically a movement that was based on the agrarian grounds. The movement was aimed to provide farmers and the agrarian workers with their true rights. There was an alliance at that time, called Farmer's Alliance and the Grange, who proceeded this movement.
The basic motivation behind this movement was that, the farmers and the agrarian workers were not being paid according to their efforts. They were given low prices for their crops. Also there was no aid for them to facilitate the farming from the government. So they initiated this movement due to the above mentioned motivation.