The correct answer is C) charred insulation and/or a blown control fuse. When a relay or contactor coil is shorted, it will draw an excessive amount of current, which can lead to the insulation on the coil becoming charred or damaged. This excessive current can also cause the control fuse to blow, as the fuse is designed to protect the circuit from such overloads. The other answer choices are incorrect: A) A higher than normal voltage reading would not be indicative of a shorted coil, as the voltage across the winding would actually be lower due to the excessive current draw. B) A resistance reading of 'infinity' would indicate an open circuit, not a short. D) A reading of 'zero' on a megger would indicate a ground fault, not necessarily a shorted coil.