What are calories? 1 they measure the amount of energy in food
2 they measure how rich in nutrients a food is
3 they measure the amount of heat a food can supply

A.

Explanation:

A calorie is a unit that is used to measure energy. The Calorie you see on a food package is actually a kilocalorie, or 1,000 calories. A Calorie (kcal) is the amount of energy needed to raise the temperature of 1 kilogram of water 1 degree Celsius.

The correct answer is B: they measure how rich in nutrients a food is.

Explanation:

Calories are measured by how many grams of carbohydrates, proteins, and fat there are in food. The nutrients in food provide calories to the body.

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