The correct answer is:
The specific heat capacities of sand and water are very different from one another.
This means that sand heats up and cools down much faster than water due to its lower specific heat capacity. Water has a high specific heat capacity, which allows it to absorb a lot of heat without a significant increase in temperature. As a result, on a hot day, the sand can become much hotter than the water, even though they are both exposed to the same sunlight.