Which statement describes a difference between insulators and conductors?

a. Insulators have high resistance, while conductors have low resistance.
b. Insulators have high conductivity, while conductors have low conductivity.
c. Insulators are made of metallic materials, while conductors are not.
d. Insulators can transmit electric current, while conductors cannot.

A. Insulators have high resistance, while conductors have low resistance.