At unity power factor, armature reaction of an alternator is:

The correct answer is option 2):(distortion of main flux)

Armature reaction:

• The effect of armature (stator) flux on the flux produced by the rotor field poles is called armature reaction. It depends on the power factor i.e. the phase relationship between the terminal voltage and armature current.
• The armature reaction flux is constant in magnitude and rotates at a synchronous speed
• At unity power factor load, the armature reaction is cross-magnetizing (distortional)
• At lagging power factor load, the armature reaction is partly demagnetizing and partly cross-magnetizing; At zero power factor lagging load, it is purely demagnetizing and the induced emf will get decreased
• When the generator supplies a load at the leading power factor the armature reaction is partly magnetizing and partly cross-magnetizing; At zero power factor leading load, it is purely magnetizing and the induced emf will get increased