Mark the example which is not correct

Options

A. Non-combustible heavy liquid used as fire extinguisher - `C Cl_(4)`
B. Blocks used to shield radioactive materials- lead
C. Element which has property of leaving mark on paper - graphite
D. A gas in solid form used as a refrigenrant- carbon monoxide

Explanation

To solve the question "Mark the example which is not correct," we need to analyze each option provided and determine which one does not fit the criteria or is factually incorrect.

### Step-by-Step Solution:

1. **Analyze Option A:**
- **Statement:** A non-combustible heavy liquid used as a fire extinguisher.
- **Example:** CCl4 (Carbon Tetrachloride)
- **Evaluation:** Carbon Tetrachloride is indeed a non-combustible liquid and has been used historically as a fire extinguisher.
- **Conclusion:** This option is correct.

2. **Analyze Option B:**
- **Statement:** Block used to seal radioactive materials.
- **Example:** Lead
- **Evaluation:** Lead is a dense metal that is effective at blocking radiation, making it suitable for sealing radioactive materials.
- **Conclusion:** This option is correct.

3. **Analyze Option C:**
- **Statement:** Element which has the property of laying mark on paper.
- **Example:** Graphite (which is a form of Carbon)
- **Evaluation:** Graphite is used in pencils to write on paper, as it leaves a mark.
- **Conclusion:** This option is correct.

4. **Analyze Option D:**
- **Statement:** A gas in solid form used as a refrigerant.
- **Example:** Carbon Monoxide
- **Evaluation:** Carbon Monoxide (CO) is a gas and is not used as a refrigerant in its solid form. The correct example should be Carbon Dioxide (CO2), which can exist as dry ice (solid form) and is used as a refrigerant.
- **Conclusion:** This option is incorrect.

### Final Answer:
- The example which is not correct is **Option D**: A gas in solid form used as refrigerant (Carbon Monoxide).

---