Which of the following is a path function?(a) Internal energy(b) enthalpy(c) work(d) entropy

To solve this question, let's first understand the distinction between **path functions** and **state functions**:

- **State functions** depend only on the initial and final states of a system, not on the path taken to reach those states. Examples include internal energy, enthalpy, and entropy.

- **Path functions**, on the other hand, depend on the specific path taken between two states. Work and heat are common examples of path functions because their values depend on how the process is carried out.

### Analyzing the options:

1. **Internal energy** (\( U \)): This is a state function because it depends only on the state of the system (i.e., temperature, volume, etc.) and not on how the system got to that state.

2. **Enthalpy** (\( H \)): Enthalpy is also a state function, as it is defined in terms of state variables (internal energy, pressure, and volume).

3. **Work** (\( W \)): Work is a path function because the amount of work done depends on how the system transitions between two states (e.g., whether the process is carried out reversibly or irreversibly).

4. **Entropy** (\( S \)): Entropy is a state function because it depends only on the initial and final states of the system.

### Conclusion:
The correct answer is **(c) work**, as it is a path function.