increasing the emf of the generator

increasing the counter emf

reducing the strength of the main field flux

reducing the sparking at the commutator segment

due to over commutation

due to under commutation

Both 1) due to over commutation and 2) due to under commutation

Neither "A" nor "B"

generator will build up maximum voltage

generator will generate maximum voltage

generator will not build up the voltage

field coils will burn

slow down the speed of the machine

decrease the output voltage

increase the output voltage

overheat the commutator and wear out the surface

increase the induced e.m.f.

reduce the eddy current loss

reduce the copper loss

reduce the armature reaction effect