When a negatively charged plastic rod touches a metal sphere, the negative charges (electrons) from the rod will transfer to the metal sphere. Since like charges repel and opposite charges attract, the excess negative charge will distribute itself across the surface of the sphere to minimize repulsion between the electrons.
In the case of a conducting sphere, the negative charges will spread out evenly across the sphere's surface, as charges in a conductor always seek to reach equilibrium and will move until they are evenly distributed.
Therefore, the correct answer is:
They spread out evenly.