I believe the answer is A. Don't trust me though, lol.
A. A UNIT OF ENERGY SUPPLIED BY FOOD.
A calorie is a unit of energy. Historically, scientists have defined "calorie" to mean a unit of energy or heat that could come from a variety of sources, such as coal or gas. In a nutritional sense, all types of food — whether they are fats, proteins, carbohydrates or sugars — are important sources of calories, which people need to live and function.
Digestion<span> begins in the mouth with chewing and ends in the small intestine. As food passes through the GI </span>tract, it mixes withdigestive<span> juices, causing large molecules of food to break down into smaller molecules.
found at
</span>Your Digestive System and How It Works | National Institute of ...<span>https://www.niddk.nih.gov/health-information/health...digestive-system/.../anatomy.aspx</span>
