`(-- CH_2 - underset(CH_3)underset(|) overset(CH_3)overset(|)C-CH_2 - underset(CH_3)underset(|)overset(CH_3)overset(|)C--)_n` is a polymer having monomer units.

Options

A.
B.
C.
D.

Explanation

To solve the question regarding the polymer structure and its monomeric units, we can follow these steps:

### Step 1: Identify the Structure of the Polymer
The given polymer structure is represented as:
`(-- CH2 - CH(CH3) - C - CH2 - CH(CH3) - C--)_n`

This indicates a repeating unit (monomer) that is linked together to form the polymer.

### Step 2: Analyze the Monomeric Unit
To find the monomeric unit, we need to break down the repeating unit in the polymer. The repeating unit can be identified as:
`CH2 - C(CH3) - C - CH2 - C(CH3) - C`

From this, we can see that the monomeric unit consists of:
- A carbon chain with branching (due to the methyl groups, CH3).
- The presence of double bonds can also be inferred from the structure.

### Step 3: Determine the Type of Polymerization
Next, we need to determine if this polymer is formed through addition polymerization or condensation polymerization.
- **Addition polymerization** occurs when unsaturated monomers (like alkenes) react to form a polymer without the loss of any small molecules.
- **Condensation polymerization** involves the loss of small molecules (like water) during the formation of the polymer.

Given that the structure contains double bonds and forms a long chain without the loss of any small molecules, we can conclude that this polymer is formed through **addition polymerization**.

### Step 4: Identify the Monomer
The monomeric unit that leads to the polymer structure can be identified as:
`C=C(CH3)2`
This represents a simple alkene with two methyl groups attached to the same carbon, which can undergo addition polymerization to form the polymer.

### Step 5: Conclusion
Thus, the monomeric unit of the given polymer is:
`C=C(CH3)2`