The resistance of mercury becomes almost zero at:

Options

A. 4 K
B. 10 K
C. 20 K
D. 25 K

Answer

To determine at what temperature the resistance of mercury becomes almost zero, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Superconductivity**:
- Superconductivity is a phenomenon where a material exhibits zero electrical resistance below a certain temperature known as the transition temperature.

2. **Identifying the Transition Temperature for Mercury**:
- Mercury is a metal that becomes a superconductor at very low temperatures. The transition temperature for mercury is typically in the range of 2 to 5 Kelvin.

3. **Finding the Exact Temperature**:
- Within the range of 2 to 5 Kelvin, we can specify that the resistance of mercury becomes almost zero when it reaches temperatures around this range.

4. **Selecting the Correct Temperature**:
- Among the options provided, if one of the options is 4 Kelvin, this falls within the range of 2 to 5 Kelvin, indicating that at this temperature, mercury will exhibit almost zero resistance.

5. **Conclusion**:
- Therefore, the resistance of mercury becomes almost zero at approximately 4 Kelvin.

### Final Answer:
The resistance of mercury becomes almost zero at 4 Kelvin.

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