How many windings are present in auto transformers?

The correct answer is option 2

Auto-Transformer:

• An auto-transformer is a type of electrical transformer with only one winding
• .The “auto” prefix refers to the single coil acting alone (Greek for “self”) – not to any automatic mechanism.
• An autotransformer is similar to a two-winding transformer but varies in the way the primary and secondary winding of the transformer are interrelated.
• In an autotransformer, one single winding is used as the primary winding as well as the secondary winding.
• But in two windings transformers, two different windings are used for primary and secondary purposes.
• A circuit diagram of the auto-transformer is shown below