The correct answer is D: between 2 and 2 1/2 bags of food per cow. This is because if you divide 9 bags of food by 5 cows, you get 1.8 bags of food per cow. Since you can't feed a cow half a bag of food, you need to round up to the nearest whole number, which is 2 bags of food per cow. Therefore, each cow ate between 2 and 2 1/2 bags of food.