Fact 1: Electrical current running through a wire causes that wire to heat up.

Fact 2: Copper is used in wires and such.

Given the two facts above, answer the question "What can run through copper, causing it to heat up?" with the following options: 
- activation energy
 - oxygen
 - water
 - an electron lens
 - electromagnetic energy
 - ice
 - hydrogen and oxygen
 - electrical current


 

        electrical current 