How do the views of the speaker's neighbor in "Mending Wall" help develop its central idea?

The neighbor's insistence that good fences make good neighbors is what pushes the speaker to suggest they replace the wall with a fence.

The fact that the neighbor suggests that rebuilding the wall is foolish is what makes the speaker change his position.

The neighbor's belief in the need for a wall is why the two men must go through the trouble of rebuilding this one.

The fact that the neighbor blames hunters for wrecking the wall is the source of the disagreement the men have over the wall.