The correct answer is C) The temperature of the water will increase; the temperature of the solid will decrease.
In fact, the solid is at higher temperature, so when it is put inside the water it starts to release heat to the water. As a result, the temperature of the solid decreases, and since the heat is absorbed by the water, the temperature of the water increases. This process continues until the water and the solid reach thermal equilibrium (i.e. until they reach same temperature).
