Fact 1: Energy is used for heating a building by a heating system.

Fact 2: Radiators are used to heat the building, The energy source is oil.

Given the two facts above, answer the question "What do radiators use to heat buildings?" with the following options: 
- coal
 - CFCs
 - Solar power
 - Oil
 - Oxygen
 - hot
 - Hydrogen
 - fuse


 

    Oil     