B.to illustrate the power struggle that Napoleon will likely win. This is the correct option.
Snowball and Napoleon disagree with each other all the time. Snowball wants to build a windmill but Napoleon wants to work on food production. Snowball wants to attack the other farms but Napoleon wants to defend their own farm. Finally, the farm gets organised to vote for the windmill but Napoleon plots against the results and has Snowball expelled from the farm. The farmers would have voted for the construction of the windmill, but Napoleon stopped this from happening. Napoleon has become the chief and has started his path to power.
These options are not right:
A.to demonstrate that Snowball is more creative than Napoleon. ( The focus is on power struggle not on creativity).
C.to reveal Napoleon's real feelings about plans for the windmill. ( His feelings have always been different from Snowball's. This is not an exception. Napoleon has always despised Snowball).
D.to show the interest of the rest of the farm in Snowball’s windmill ( The rest of the farm have got really interested in the plans , but this is not the point in this passage. The animals are just listening to Snowball's ideas and looking at his plans).