The correct answer is B: They have many free electrons. Metals are generally good conductors of electricity because they have many free electrons - electrons that are not tightly bound to individual atoms and can move freely through the material. In metals, the outer electrons of atoms are shared among all atoms in a 'sea of electrons.' These free electrons can move easily when a voltage is applied, creating current flow. This is why metals like copper, aluminum, and silver are excellent conductors - they have many free electrons available to carry current. The more free electrons a material has, the better it conducts electricity. This is why copper wire is used for electrical connections - it has many free electrons and low resistance.