One day, when I had to leave for office in a hurry, I had a definite quantity of rice with me, which had just been cooked and placed in a bowl. Which of the following will be the better option to cool it quickly?

The fastest way to cool the rice is to maximize heat transfer through evaporation and convection simultaneously. Placing the hot rice bowl in a larger bowl of water at room temperature allows rapid heat conduction from the rice bowl into the surrounding water (water has high specific heat and conducts heat well from the metal/ceramic surface), while running a fan at full speed over it accelerates evaporation from the water surface, drawing latent heat away and cooling the system rapidly. The fan alone (option a, b) or water alone (option d) would each be slower than the combined effect. Hence option (c) is the most effective.