The correct answer is: D. Load flow, short-circuit and stability.

An AC network analyzer is a computer program that solves the equations of electric power systems. It can be used to solve problems of load flow, short-circuit, and stability.

Load flow is the process of determining the steady-state power flow in an electric power system. It is used to determine the voltage and current at all nodes in the system, as well as the power flow on all lines.

Short-circuit analysis is the process of determining the current that would flow in an electric power system if a short circuit occurred. It is used to design protective devices, such as circuit breakers, to ensure that the system remains safe during a short circuit.

Stability analysis is the process of determining whether an electric power system will remain stable under various operating conditions. It is used to design control systems to ensure that the system remains stable even in the event of disturbances.

AC network analyzers are used by power system engineers to design, analyze, and operate electric power systems. They are an essential tool for the safe and reliable operation of electric power systems.

Here is a brief explanation of each option:

• Load flow is the process of determining the steady-state power flow in an electric power system. It is used to determine the voltage and current at all nodes in the system, as well as the power flow on all lines.
• Short-circuit analysis is the process of determining the current that would flow in an electric power system if a short circuit occurred. It is used to design protective devices, such as circuit breakers, to ensure that the system remains safe during a short circuit.
• Stability analysis is the process of determining whether an electric power system will remain stable under various operating conditions. It is used to design control systems to ensure that the system remains stable even in the event of disturbances.