Which of the following is a good insulator?

A. wire

B. doorknob

C. plastic

D. nickel

C; Because It cannot allow things to pass through it

An insulator is a material or substance that does not allow other substances such as electricity, light, heat etc. to pass through easily. This is why wire cables are wrapped in plastic because it does not allow electricity and heat to pass through. SO the answer is C - Plastic