Well and rice and egg are both correct. If you think about it, rice is more of a solid. The rest are liquidly is some sort of way. But then, egg is correct because its the only item that has a yellow with white color to it. The rest are white. Rice by itself is not white. But nowadays when people think about rice, they think of white rice.
Eggs, milk and cream all come from animals, while rice is a plant.
The correct answer is egg. It's the only word that's listed in singular form. You can ask for an egg, but you don't ask for a rice/milk/cream.
Egg is a countable noun while the others are all uncountable