Two systems are in thermal equilibrium. The quantity which is common for them is

Options

A. heat
B. specific heat
C. temperature
D. latent heat

Explanation

To solve the question, "Two systems are in thermal equilibrium. The quantity which is common for them is," we need to understand the concept of thermal equilibrium and the relevant quantities involved.

### Step-by-Step Solution:

1. **Understanding Thermal Equilibrium**:
- Thermal equilibrium occurs when two systems are at the same temperature and there is no net flow of heat between them.

2. **Identifying the Options**:
- The options given are:
a) Heat
b) Specific Heat
c) Temperature
d) Latent Heat

3. **Analyzing Each Option**:
- **Heat**: This refers to the energy transferred between systems due to a temperature difference. In thermal equilibrium, the heat flow is zero, but the amount of heat in each system can be different.
- **Specific Heat**: This is a property of a material that indicates how much heat is required to change the temperature of a unit mass of the substance by one degree. It varies from one substance to another and is not necessarily the same for both systems.
- **Temperature**: This is a measure of the average kinetic energy of the particles in a system. In thermal equilibrium, both systems must have the same temperature.
- **Latent Heat**: This is the heat required for a phase change of a substance at constant temperature. It is not relevant to the concept of thermal equilibrium directly.

4. **Conclusion**:
- Since the definition of thermal equilibrium states that both systems must be at the same temperature, the common quantity for two systems in thermal equilibrium is **Temperature**.

### Final Answer:
The quantity which is common for the two systems in thermal equilibrium is **Temperature**.

---