The highest calorific value is found in:
A. Proteins
B. Fats
C. Vitamins
D. Carbohydrates

Hint: Calorific value is defined as the amount of energy produced by the complete combustion of a fuel or material. It is measured in units of energy per amount of material like $kJ/kg$.

Complete step by step answer:
Complete step by step solution:
Calorific value is the amount of energy available from an item of food when digested, mostly from carbohydrates and fats. It is the amount of energy produced or released when $1kg$of fuel burns or any other substance is burnt in the presence of oxygen and the products of combustion are cooled to standard temperature pressure. It is very important to know about the calorific value of fuel to carry out our day to day activities and it helps us to determine the amount of energy we transport. The gas suppliers and shippers require the knowledge of calorific value to bill gas consumers. The highest calorific value is also known as gross energy or gross calorific value. It is defined as the quantity of heat released by a specified quantity once it is combusted and the products have returned to a temperature of $25^\circ C$. Ethanol and fats have the highest amount of calorific value per gram i.e. $29$ and $37$ kilojoules per gram or $6.9$ and $8.8$kcal/g respectively and proteins and most carbohydrates both have about $17kJ/g$ or $4kcal/g$. Therefore, fats have the highest calorific value among all.

So, the correct answer is Option A.

Note: Fat is the most important and biggest source of energy and chocolate has a high calorific value. Thus, it should be consumed in moderation.