Which of the following is a good insulator?
a. wire

b. doorknob

c. plastic

d. nickel

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

Mg is used to measure mass

Where is the picture at