Concept:Birds have fixed eyes on the sides of their head, which limits their binocular vision.
Explanation:Birds cannot move their eyes like humans.
Their eyes are fixed and placed on opposite sides of the head.
This gives a wide view to each side but poor depth perception.
To judge distance, birds move their neck to see the same object from two slightly different angles.
Their brain then combines these two images to measure depth.
Therefore, birds move their neck often to compensate for fixed eyes.
Answer:B (the birds eyes are fixed)