Step 1: Understanding the Question:
The image shows a repeating unit of a polymer structure: $[CH_2 - C(CH_3) = CH - CH_2]_n$. We need to identify its monomer. Step 2: Detailed Explanation:
1. The repeating unit shown is that of polyisoprene (natural rubber).
2. To find the monomer, we look at the structure within the brackets. It has a 5-carbon chain with a double bond in the middle of the unit.
3. This corresponds to the polymerization of 2-methyl-1,3-butadiene.
4. The common name for 2-methyl-1,3-butadiene is Isoprene. Step 4: Final Answer:
The monomer is Isoprene.
