Which materials allow electrons to travel freely?

The correct answer is conductors. Conductors are materials that allow electrons to move freely through them, which is essential for the flow of electric current. This ability is due to the presence of free electrons in the atomic structure of these materials, typically metals like copper and aluminum. These free electrons can move easily in response to an electric field, facilitating the conduction of electricity.

In contrast, insulators are materials that do not allow electrons to flow freely. They have tightly bound electrons and do not conduct electricity well. Semiconductors, on the other hand, have properties between insulators and conductors. They can conduct electricity under certain conditions but do not allow free flow of electrons as conductors do. Dielectrics are materials that are poor conductors of electricity and are often used to insulate conductors, preventing leakage of current. This context demonstrates why conductors are the choice that accurately describes materials that permit the free movement of electrons.