A body of water where light penetrates all the way to the bottom is a ____.

• A. Reservoir
• B. Pond
• C. Lake
• D. Swamp

Answer: (B)

Light reaching the bottom means the water is shallow enough and clear enough for sunlight to illuminate the substrate, allowing photosynthesis right at the bed. Ponds are typically small and shallow, so light can penetrate to the bottom across most of the area, supporting bottom-dwelling plants and organisms. In contrast, reservoirs can be deeper and murkier, lakes often have deeper zones where light doesn’t reach the bottom, and swamps are characterized by dense vegetation and organic material that limit light penetration. Because the bottom is lit throughout, the body of water best described is a pond.