The repeating units of PTFE are

Options

A. `F_3C - CF_3`
B. `FClC = CF_2 `
C. `F_2C = CF_2`
D. none of these

Explanation

To determine the repeating units of PTFE (polytetrafluoroethylene), we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Monomer**:
The monomer for PTFE is tetrafluoroethylene, which has the chemical formula CF2=CF2. This is the starting material that will undergo polymerization to form PTFE.

2. **Understand Polymerization**:
During polymerization, the double bond in the monomer (CF2=CF2) is broken, allowing the monomers to link together. This process typically occurs under high pressure and in the presence of a catalyst.

3. **Form the Repeating Unit**:
After polymerization, the structure of PTFE consists of repeating units derived from the monomer. Each monomer contributes to the polymer chain, resulting in a structure where the double bond is replaced by single bonds.

4. **Write the Repeating Unit**:
The repeating unit of PTFE can be represented as -CF2-CF2-. This indicates that each unit consists of two carbon atoms, each bonded to two fluorine atoms.

5. **Select the Correct Option**:
From the options provided, the correct repeating unit of PTFE is CF2-CF2, which corresponds to option C.

### Final Answer:
The repeating units of PTFE are CF2-CF2 (option C).

---