William Gilbert Discovered Many Important Properties of Magnets

William Gilbert discovered many important properties of magnets. Which of the following was not among Gilbert's findings?

A) Every magnet has at least two poles.
B) If magnetic poles are alike, they repel each other.
C) Steel rods can be magnetized by stroking them with a lodestone.
D) Electric currents can be produced by changing magnetic fields.
E) Iron's magnetism can be destroyed by heating.