Read the excerpt from Animal Farm. The whole farm was deeply divided on the subject of the windmill. Snowball did not deny that to build it would be a difficult business. Stone would have to be carried and built up into walls, then the sails would have to be made and after that there would be need for dynamos and cables. (How these were to be procured, Snowball did not say.) But he maintained that it could all be done in a year. And thereafter, he declared, so much labour would be saved that the animals would only need to work three days a week. Napoleon, on the other hand, argued that the great need of the moment was to increase food production, and that if they wasted time on the windmill they would all starve to death. The animals formed themselves into two factions under the slogan, "Vote for Snowball and the three-day week” and "Vote for Napoleon and the full manger."

Why does Snowball want to build a windmill?

He wants to compel the animals to work harder.
He wants to increase food production immediately.
He wants to find a use for the stone on the farm.
He wants to make the farm run more efficiently.