Which of the listed conditions will occur if dirt and grease are allowed to accumulate between the commutator segments of a DC motor?

Correct Answer: Option B — A partial short circuit.

Conductive carbon dust, oil, and moisture bridging mica undercuts between commutator bars create tracking paths. This conductive bridge causes a partial short circuit, leading to severe localized heating, increased brush sparking, accelerated copper wear, and potential flashover under operational load.