Which one of the following molecules can serve as a monomer for an addition polymer?

Options

A. `H_2C=CH-C_6H_5`
B. `H_2C=CHCN`
C. `ClCH=CH_2`
D. All of these

Answer

To determine which molecule can serve as a monomer for an addition polymer, we need to identify if the molecule contains a double or triple bond. Addition polymers are formed when monomers with these types of bonds undergo a reaction that opens the bond, allowing them to link together into a long chain.

### Step-by-Step Solution:

1. **Identify the Structure of Each Molecule**:
- Look at the provided options and identify their molecular structures. We need to check if they contain double or triple bonds.

2. **Check for Double or Triple Bonds**:
- For each molecule, verify if there is a double bond (C=C) or a triple bond (C≡C). These bonds are essential for addition polymerization.

3. **Analyze Each Molecule**:
- **Molecule 1**: If it has a double bond, it can undergo addition polymerization.
- **Molecule 2**: Check for a double bond; if present, it can also serve as a monomer.
- **Molecule 3**: Again, check for a double bond.
- **Molecule 4**: Confirm the presence of a double bond.

4. **Determine the Repeating Unit**:
- For each molecule that has a double bond, illustrate how the double bond can break and how the monomers can link together to form a repeating unit.

5. **Conclusion**:
- If all the molecules contain double bonds, then all of them can serve as monomers for addition polymers.

### Final Answer:
All of the given molecules can serve as monomers for addition polymers because they all contain double bonds.