DC Motors
The plugging gives the

Smallest torque braking
Highest torque braking
Zero torque braking
None of the listed here

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DC Motors
If a D.C. shunt motor is working at no load and if shunt field circuit suddenly opens

This will make armature to take heavy current, possibly burning it
This will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses
Nothing will happen to the motor
Motor will run at very slow speed

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