Question

line after line and uttering little whimpers of excitement. gradually the plans grew into a complicated mass of cranks and cog - wheels, covering more than half the floor, which the other animals found completely unintelligible but very impressive.
why does snowball go to the shed so often?
he is planning the windmill.
he wants to be a famous artist.
he wants to help napoleon.
he is tired of working hard.

Explanation:

In the context of "Animal Farm", Snowball goes to the shed often to plan the windmill, as the text describes plans with cranks and cog - wheels (related to the windmill design). The other options are inconsistent with the story: he isn't aiming to be a famous artist, he and Napoleon have conflicts so he doesn't want to help Napoleon, and he is actively working on the windmill plan not tired of working hard.

Answer:

A. He is planning the windmill.