The four elements called "Big-four" which make up 95% of all elements found in a living system are -

Options

A. C, H, O, N
B. C, H, O, P
C. C, H, O, S
D. C, N, O, P

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the four elements that constitute 95% of all elements found in living systems, commonly referred to as the "Big Four".

2. **Identifying the Fundamental Unit of Life**: The fundamental unit of life is the cell. Cells are composed of various components, including cell walls, cell membranes, cytoplasm, and organelles.

3. **Recognizing the Role of Biomolecules**: The components of cells are made up of biomolecules, which include carbohydrates, proteins, and lipids. These biomolecules are essential for the structure and function of cells.

4. **Determining the Key Elements in Biomolecules**: The primary elements that make up biomolecules are:
- **Carbon (C)**: A key component of all organic molecules.
- **Hydrogen (H)**: Found in all biomolecules and is essential for energy.
- **Oxygen (O)**: Vital for respiration and is a part of many biomolecules.
- **Nitrogen (N)**: An essential component of amino acids and nucleic acids.

5. **Conclusion**: The four elements that make up 95% of all elements found in living systems are Carbon, Hydrogen, Oxygen, and Nitrogen.

**Final Answer**: The four elements called the "Big Four" are Carbon, Hydrogen, Oxygen, and Nitrogen.

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