Nutrition labels provide information about all of the following except
calories.
vitamins.
serving size.
preparing food.

The correct answer is D, Preparing Food.

Explanation:

Food items that are sold in markets have a section that provides information about the nutritional values of the food inside it. This section has the information about the calories of the proportion of the food item, Vitamins in the food, carbs, proteins, fats, and about the serving size of the food item. But such sections does not provide information about how to prepare the food inside it. So Option D is quite a sure answer.  

it keeps oxygen levels low throughout the body