The correct answer is B) Heeling magnets. Heeling magnets are the only magnetic compass correctors that can correct for both permanent and induced effects of magnetism. Permanent magnetism is a fixed magnetic field that remains constant, while induced magnetism is a temporary magnetic field that changes as the ship's heading changes. Heeling magnets can compensate for both of these effects, making them the most effective compass correctors. The other options, such as athwartships magnets, fore-and-aft magnets, and quadrantal spheres, are designed to correct for specific types of magnetic effects, but they do not address both permanent and induced magnetism simultaneously.