The substance which possesses zero resistance at 105 K:

Options

A. Hg
B. `YBa2Cu_(3)O_(7)`
C. `Nb_(3)Ge`
D. All of these

Answer

To determine the substance that possesses zero resistance at 105 K, we need to understand the concept of critical temperature and its relationship with resistance in superconductors.

### Step-by-Step Solution:

1. **Understanding Zero Resistance**:
- Zero resistance occurs in materials known as superconductors when their temperature is below a certain threshold called the critical temperature (Tc).

2. **Identify the Given Temperature**:
- The temperature provided in the question is 105 K.

3. **Critical Temperature of Substances**:
- We need to compare the given temperature (105 K) with the critical temperatures of various substances to determine which one exhibits zero resistance at this temperature.
- For example:
- Mercury (Hg) has a critical temperature of approximately 1750 K.
- YBa2Cu3O7 (YBCO) has a critical temperature of about 108.1 K.
- Niobium (Nb3Sn) has a critical temperature of around 23 K.

4. **Comparison of Temperatures**:
- **Mercury (Hg)**:
- Critical Temperature = 1750 K
- 105 K is much less than 1750 K, but the difference is too large to consider it a superconductor at this temperature.
- **YBa2Cu3O7 (YBCO)**:
- Critical Temperature = 108.1 K
- 105 K is less than 108.1 K, and the difference is small, indicating that it can exhibit zero resistance.
- **Niobium (Nb3Sn)**:
- Critical Temperature = 23 K
- 105 K is greater than 23 K, so it cannot exhibit zero resistance.

5. **Conclusion**:
- The only substance that meets the criteria of having a critical temperature higher than the given temperature (105 K) is YBa2Cu3O7 (YBCO). Therefore, this is the substance that possesses zero resistance at 105 K.

### Final Answer:
The substance which possesses zero resistance at 105 K is **YBa2Cu3O7 (YBCO)**.