Freerice.com - Donate rice for free (no gimmick just do it)

Not too long ago, I was looking for some of the top websites (research for creating my own) and I found this beautifully simple site called freerice.com. Basically you just play trivia games and for every question you get right, 10 grains of rice are donated on your behalf. I've found no reason to believe that this is a fraud or that they aren't making full good on their promise. The rice is provided by the ads at the bottom of the page. What an amazing and uncomplicated idea. A bonus is that the games are guiltlessly (new word) addictive (although identifying the eastern European countries can be frustrating...so bunched together).










Which could it be?