Which of the following is not a biologically active polymer?

Options

A. Starch
B. Collagen
C. Water
D. DNA

Explanation

To determine which of the following is not a biologically active polymer, we need to analyze each option provided: starch, collagen, water, and DNA.

### Step-by-Step Solution:

1. **Understanding Polymers**:
- A polymer is a large molecule made up of repeating subunits known as monomers. These can be natural or synthetic and play various roles in biological systems.

2. **Analyzing Starch**:
- Starch is a polysaccharide made up of glucose monomers. It serves as an energy storage molecule in plants. Since it is composed of repeating units (glucose), starch is a biologically active polymer.

3. **Analyzing Collagen**:
- Collagen is a structural protein that forms a matrix in connective tissues. It is made up of amino acid monomers and is essential for the integrity of tissues. Therefore, collagen is also a biologically active polymer.

4. **Analyzing Water**:
- Water (H2O) is a simple molecule and not a polymer. It does not consist of repeating monomer units and does not function as a polymer in biological systems. Thus, water is not a biologically active polymer.

5. **Analyzing DNA**:
- DNA (deoxyribonucleic acid) is a polymer made up of nucleotide monomers. It carries genetic information and is crucial for the functioning of living organisms. Therefore, DNA is a biologically active polymer.

6. **Conclusion**:
- Among the options provided, starch, collagen, and DNA are all biologically active polymers, while water is not. Hence, the answer to the question is **water**.

### Final Answer:
**Water is not a biologically active polymer.**