The physical quantity that determins whether or not a given system A is in thermal equilibrium with another system B is called

Options

A. Pressure
B. Volume
C. temperature
D. none of these

Explanation

To determine whether a given system A is in thermal equilibrium with another system B, we need to identify the physical quantity that governs this relationship. The concept of thermal equilibrium is fundamentally linked to temperature.

### Step-by-Step Solution:

1. **Understanding Thermal Equilibrium**:
- Thermal equilibrium occurs when two systems are in contact and there is no net heat flow between them. This means that the systems have reached a state where their temperatures are equal.

2. **Identifying the Relevant Physical Quantity**:
- The question asks for the physical quantity that determines thermal equilibrium. The key here is to recognize that thermal equilibrium is defined by the equality of temperature between the two systems.

3. **Evaluating the Options**:
- The options provided are:
1. Pressure
2. Volume
3. Temperature
4. None of these
- Among these options, pressure and volume do not determine thermal equilibrium. They can vary independently of temperature.

4. **Conclusion**:
- Since thermal equilibrium is defined by equal temperatures, the correct answer is **temperature**. If the temperatures of systems A and B are the same, they are in thermal equilibrium.

### Final Answer:
The physical quantity that determines whether or not a given system A is in thermal equilibrium with another system B is **temperature**.

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