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

Fact 2: Raw coal can be burned to produce electricity.

Given the two facts above, answer the question "What can cause a wire to heat up?" with the following options: 
- soil
 - ice
 - waves
 - LEDs
 - motors
 - coal
 - silt
 - copper


 

      coal   