Phosphorus is always present in

Options

A. Protein
B. DNA and RNA
C. Amino acid
D. starch

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks where phosphorus is always present. We need to analyze the options given: protein, DNA and RNA, amino acid, and starch.

2. **Analyzing Each Option**:
- **Protein**: Proteins are made up of amino acids and primarily contain elements like carbon, hydrogen, oxygen, nitrogen, and sulfur. Phosphorus is not a primary component of proteins.
- **Amino Acid**: Amino acids are the building blocks of proteins and do not typically contain phosphorus.
- **Starch**: Starch is a carbohydrate made up of glucose units and primarily contains carbon, hydrogen, and oxygen. Phosphorus is not a component of starch.
- **DNA and RNA**: Both DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are nucleic acids that contain phosphorus in their backbone structure. When these nucleic acids break down, they release phosphorus.

3. **Conclusion**: Since phosphorus is a key component of nucleic acids (DNA and RNA), the correct answer to the question is **DNA and RNA**.

**Final Answer**: Phosphorus is always present in **DNA and RNA**.

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