The most likely obstacle to your movement while taking a walk in the woods would be a boulder across the path (OA). An obstacle is something that blocks your way or makes it difficult to move forward. In this scenario, a boulder across the path would physically impede your progress, requiring you to find a way around it or climb over it to continue your walk.
Sunlight peeking through trees (OB), a view of a lake from the hilltop (OC), and a light breeze that rustles the leaves (OD) are not obstacles to your movement because they do not hinder your ability to walk through the woods. While they may create certain atmospheric or visual effects, they do not directly block your path or make it challenging to move forward.
