Which of the following is the main source of energy in living ?

Options

A. Fat
B. Protein
C. Carbohydrate
D. Vitamin

Answer

To determine the main source of energy in living organisms, we need to analyze the options provided: fats, proteins, carbohydrates, and vitamins.

### Step-by-Step Solution:

1. **Understanding Fats**:
- Fats are oily substances stored in the body, primarily under the skin and around organs. They serve as a source of energy but are not the primary energy source for immediate use.

**Hint**: Consider the role of fats in energy storage rather than immediate energy supply.

2. **Understanding Proteins**:
- Proteins are made up of amino acids linked by peptide bonds. They have a high molecular mass and are essential for various bodily functions, including building tissues and enzymes. However, they are not primarily used for energy.

**Hint**: Think about the primary functions of proteins beyond energy supply.

3. **Understanding Carbohydrates**:
- Carbohydrates are essential nutrients that the body converts into glucose. Glucose is a primary energy source for cells, especially for brain and muscle function. Carbohydrates consist of carbon, hydrogen, and oxygen, and their general formula is \( C_n(H_2O)_n \).

**Hint**: Recall how the body utilizes carbohydrates for immediate energy needs.

4. **Understanding Vitamins**:
- Vitamins are organic compounds required in small amounts for various biochemical functions. They do not provide energy directly but are crucial for metabolic processes.

**Hint**: Consider the role of vitamins in metabolism rather than energy provision.

5. **Conclusion**:
- Among the options provided, carbohydrates are the main source of energy in living organisms. They are readily converted into glucose, which is utilized by cells for energy.

### Final Answer:
**The main source of energy in living organisms is option C: Carbohydrates.**