After 24 hours with the temperature water remains at 24 c. What property of water explains why the temperature did not drop all the way back to the original temperature

well, that's easy; the answer's c, "it reduces contamination of the water and substrate of the estuary."

a physical change is being made.

your body is trying to warm itself up. or more precisely, sensors in your skin send messages to your brain to generate heat to your body.