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 known as the "big four" that make up 95% of all elements found in living systems.

2. **Identifying Living Systems**: Living systems are primarily composed of cells, which are the basic structural and functional units of life.

3. **Analyzing Cell Composition**: Cells contain various biological compounds such as proteins, lipids, and carbohydrates.

4. **Determining Key Elements**: To understand what these biological compounds are made of, we can look at their chemical formulas. The main elements that constitute these compounds are:
- Carbon (C)
- Hydrogen (H)
- Oxygen (O)
- Nitrogen (N)

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

6. **Final Answer**: The correct answer is Carbon, Hydrogen, Oxygen, and Nitrogen.

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