The surface of a lake is frozen in severe winter, but the water at its bottom is still liquid. What is the reason?

1. Water exhibits anomalous behavior; its density is maximum at 4°C. 2. As the surface water of a lake cools during winter, it becomes denser and sinks. 3. This process continues until the entire water body reaches 4°C. 4. Further cooling of the surface water below 4°C makes it *less* dense. 5. This colder, less dense water stays at the surface and eventually freezes into ice at 0°C. 6. The denser water at 4°C remains at the bottom in its liquid state. 7. While ice being a bad conductor of heat (Option A) helps insulate the water below once the surface is frozen, the fundamental reason why the warmer water stays at the bottom is the maximum density of water at 4°C (Option C). 8. Option (B) is incorrect because heat is lost from the surface to the colder air.