Ryder has been visiting his favorite park for ten years. Recently, he noticed that the large boulder in the center of the park has gotten smaller and smoother in some places. Why has the boulder changed? A. Wind and water have weathered the boulder, wearing away at its surface. B. The weight of the boulder has caused its rock particles to compress. C. The rock particles in the boulder have cemented into thinner layers. D. The heat of the Sun evaporated out the water, causing the boulder to shrink.