Name the monomer present in the following polymerA. Polyvinyl chlorideB. Natural rubber.

To identify the monomers present in the given polymers, let's look at each one individually:

### A. Polyvinyl Chloride (PVC)
- **Monomer**: The monomer for Polyvinyl Chloride is **vinyl chloride**.
- **Chemical Structure**: The structure of vinyl chloride is \( \text{CH}_2=\text{CHCl} \).
- **Polymerization Process**: PVC is formed by the polymerization of vinyl chloride monomers through a process called addition polymerization. During this process, the double bond in the vinyl chloride opens up and links together to form long chains.

### B. Natural Rubber
- **Monomer**: The monomer for natural rubber is **isoprene**.
- **Chemical Structure**: The structure of isoprene is \( \text{C}_5\text{H}_8 \), which can be represented as \( \text{CH}_2=\text{C(CH}_3)-\text{CH}=\text{CH}_2 \).
- **Polymerization Process**: Natural rubber is made from the polymerization of isoprene molecules through a process called addition polymerization. The double bonds in isoprene open up during polymerization, allowing the monomers to link together and form long polymer chains.

### Summary
- **Polyvinyl Chloride (PVC)**: Monomer is **vinyl chloride**.
- **Natural Rubber**: Monomer is **isoprene**.

This understanding of monomers is crucial for the study of polymer chemistry, as the properties of the polymer are significantly influenced by the structure and arrangement of its monomers.