Phosphorus is always present in

Options

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

Answer

To solve the question "Phosphorus is always present in", we can follow these steps:

### Step 1: Understand the question
The question asks where phosphorus is consistently found. We need to analyze the options provided to determine which one contains phosphorus.

### Step 2: Analyze the options
1. **Protein**: Proteins are made up of amino acids, which primarily contain carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur. Phosphorus is not a primary component of proteins.

2. **Amino Acids**: While amino acids are the building blocks of proteins, they do not typically contain phosphorus. They mainly consist of carbon, hydrogen, oxygen, and nitrogen.

3. **Starch**: Starch is a carbohydrate made up of glucose units. It primarily contains carbon, hydrogen, and oxygen, but no phosphorus.

4. **DNA and RNA**: These are nucleic acids that are essential for genetic information. Both DNA and RNA contain phosphorus in their backbone structure, specifically in the form of phosphate groups.

### Step 3: Identify the correct answer
Based on the analysis, the only option that consistently contains phosphorus is **DNA and RNA**. Therefore, the correct answer is:

**Phosphorus is always present in DNA and RNA.**

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

---