Fact 1: Coal is used to produce electricity by burning in coal-fire power stations.

Fact 2: Solid refined coal is easy to transport and can be used in coal-burning equipment.

Given the two facts above, answer the question "Solid materials used to produce electricity by burning in what need to be transported firs" with the following options: 
- Conifers
 - animals
 - it needs them
 - humans
 - heat energy
 - important habitats
 - power stations
 - batteries


 

       power stations  