Question

Which of the following substances act as fuel in the human body?

• A. Protein
• B. Vitamin
• C. Carbohydrate
• D. Water

Hint:

Think about which nutrient the body breaks down first, right away, to power its cells.

Answer 1

The Correct Option is C

Step 1: Understanding the Question.
The question asks which substance works as the main fuel for the body, that is, which one the body burns first to get energy for its daily work.

Step 2: Key Concept.
The body gets energy mainly from carbohydrates, fats and proteins. Among these, carbohydrates are the body's preferred and fastest source of fuel. They are broken down into glucose, which cells burn right away to make energy. The brain, muscles and red blood cells depend heavily on this glucose supply.

Step 3: Checking each option.
(A) Protein: Protein is used mainly to build and repair body tissue, not as the first choice of fuel. The body turns to protein for energy only when carbohydrate and fat stores run low.
(B) Vitamin: Vitamins do not supply energy at all. They help enzymes work properly and support many body processes, but they carry no calories of their own.
(C) Carbohydrate: Carbohydrate is broken down into glucose and used directly by cells for energy. This is the body's main and quickest fuel source.
(D) Water: Water carries no calories and cannot act as fuel. It helps carry nutrients and remove waste, but gives no energy.

Step 4: Final Answer.
Carbohydrate is the substance that acts as fuel in the human body.