To determine the correct answer to the given question, we must understand the basic structure and functioning of an alternator in electrical machines.

An alternator, also known as a synchronous generator, is designed to convert mechanical energy into electrical energy in the form of alternating current (AC). The two main components of an alternator are:

1. Rotor: This is the rotating part of the alternator. It contains a set of magnets or windings that generate a magnetic field. The rotor is mechanically driven by an engine or turbine.
2. Stator: This is the stationary part and contains the stator windings. When the rotor spins, its magnetic field induces an alternating current in these stator windings according to Faraday's law of electromagnetic induction.

Considering these components, let's analyze the options:

• Rotor winding: The rotor winding is involved in creating the magnetic field, but it is not where the electrical output is taken from.
• Commutator: Alternators do not have commutators. Commutators are typically used in DC machines to convert AC to DC.
• Field winding: The field winding is typically on the rotor, responsible for producing the magnetic field, not the electrical output.
• Stator winding: This is the correct part from which the electrical output of an alternator is taken. The AC voltage is induced in these windings when the rotor's magnetic field moves relative to them.

Hence, the correct answer is the Stator winding.

This makes option Stator winding the correct answer, as it is the component from which the electrical output is extracted in an alternator.