The correct answer is A) replaced with a satisfactory spare. A bent or distorted pump shaft should normally be replaced rather than repaired, as a distorted shaft can cause vibrations and damage to the pump and other equipment. Attempting to straighten or weld a bent shaft is generally not recommended, as this can further compromise the integrity of the shaft and may not fully restore it to proper working condition. The safest and most reliable approach is to replace the damaged shaft with a spare that is in satisfactory condition. The other options are incorrect because: B) straightening by heat and torsion may not fully restore the shaft, C) welding repairs are not the best solution for a bent shaft, and D) reconditioning by metalizing and machining is an unnecessary and potentially less effective solution compared to outright replacement.