Which of the following is a natural polymer?

Options

A. `cis-1,4-"polyisoprene"`
B. poly (Butadiene-styrene)
C. polybutadiene
D. poly (Butadiene-acrylonitrile)

Answer

To determine which of the given options is a natural polymer, we need to analyze each option based on its monomer and whether that monomer is derived from natural sources (plants or animals) or synthesized from synthetic sources.

### Step-by-Step Solution:

1. **Understand Natural Polymers**:
- Natural polymers are those that are synthesized from natural products, typically derived from plants or animals. Examples include proteins, cellulose, and rubber.

2. **Analyze Option 1: Cis-1,4-polyisoprene**:
- The monomer of cis-1,4-polyisoprene is isoprene.
- Isoprene is a natural product that is obtained from the sap of rubber trees.
- Therefore, cis-1,4-polyisoprene is a natural polymer.

3. **Analyze Option 2: Polybutadiene-styrene**:
- The monomers are 1,3-butadiene and styrene.
- Both of these monomers are derived from crude oil, which is a synthetic source.
- Thus, polybutadiene-styrene is a synthetic polymer.

4. **Analyze Option 3: Polybutadiene**:
- The monomer is butadiene, which is also derived from crude oil.
- Therefore, polybutadiene is a synthetic polymer.

5. **Analyze Option 4: Polybutadiene-acrylonitrile**:
- This polymer uses butadiene (from crude oil) and acrylonitrile as monomers.
- Since butadiene is synthetic, this polymer is also synthetic.

6. **Conclusion**:
- Among the options provided, only **Option 1: Cis-1,4-polyisoprene** is a natural polymer.

### Final Answer:
**Option 1: Cis-1,4-polyisoprene is the natural polymer.**

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