Which of the following is a biodegradable polymer ?

Options

A. `[-HN - (CH_2)_5CONH - CH_2-overset(O)overset(||)C-]_n`
B. `[-HN - (CH_2)_5-overset(O)overset(||)C-]_n`
C. `[-HN-(CH_2)_6 NHCO - (CH_2)_4 - overset(O)overset(||)C-]_n`
D.

Explanation

To determine which of the following is a biodegradable polymer, we need to analyze the given options and identify the characteristics of each polymer.

### Step-by-Step Solution:

1. **Understanding Biodegradable Polymers**:
- A biodegradable polymer is one that can break down into natural products after its purpose has been served. This breakdown typically occurs through the action of living organisms, such as bacteria.

2. **Analyzing the Options**:
- **Option A**: NH-CH2-5-CO-NH-CH2-CO
- This structure indicates the presence of an amide linkage (CONH), suggesting it is a polyamide. Specifically, this is Nylon-2-Nylon-6, which is known to be biodegradable.

- **Option B**: NH-CH2-6-CO
- This structure also shows an amide linkage, indicating it is a polyamide. This is Nylon-6, which is not biodegradable.

- **Option C**: NH-CH2-6-NH-CO-CH2-4-C=O
- This structure contains an amide linkage as well and is known as Nylon-6,6, formed from adipic acid and hexamethylene diamine. Nylon-6,6 is also not biodegradable.

- **Option D**: CO-CO-Benzene-C=O-CH2-2-O
- This structure shows an ester linkage (COO), indicating it is a polyester. Terylene, formed from terephthalic acid and ethylene glycol, is a common example of this type of polymer and is not biodegradable.

3. **Conclusion**:
- After analyzing all options, **Option A (Nylon-2-Nylon-6)** is identified as the biodegradable polymer.

### Final Answer:
The biodegradable polymer among the options is **Option A: NH-CH2-5-CO-NH-CH2-CO (Nylon-2-Nylon-6)**.

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