Question

what is an insulator?
a material that prevents the flow of electrons
a material that stores electrical charge
a device that generates static electricity
a material that allows electrons to flow freely

Explanation:

In physics (a subfield of Natural Science), an insulator is defined as a material with very high electrical resistance, which means it does not allow electrons (electric charge carriers) to flow easily through it. The other options are incorrect: a material that allows electrons to flow freely is a conductor, a device generating static electricity is not an insulator, and a material storing electrical charge is a capacitor - like component, not an insulator.

Answer:

A. A material that prevents the flow of electrons