Which of the following generating machine will offer constant voltage on all loads?

The correct answer is:

**C. Level compounded generator**

### Explanation:

- **Self-Excited Generator**: The voltage of a self-excited generator tends to decrease as the load increases due to the drop in field excitation caused by the reduction in terminal voltage.

- **Separately Excited Generator**: While a separately excited generator can maintain a more constant voltage than a self-excited one, it still experiences some voltage drop under load due to armature reaction and internal resistance.

- **Level Compounded Generator**: A level compounded generator is designed to maintain a nearly constant voltage across all loads. It achieves this by combining the characteristics of both series and shunt windings. The series winding compensates for the voltage drop caused by the load, keeping the terminal voltage nearly constant.

- **All of the Above**: This option is incorrect because not all the generators listed maintain a constant voltage under varying loads.

### Conclusion:

The **level compounded generator** is specifically designed to offer a constant voltage across varying loads, making it the correct choice.