Gap-fill exercise

Fill in all the gaps, then press "Check" to check your answers. Use the "Hint" button to get a free letter if an answer is giving you trouble. You can also click on the "[?]" button to get a clue. Note that you will lose points if you ask for hints or clues!

Energy gives the ability to do
Wind, sun and water energy are classed as
Fossil fuel energy is classed as
The principal of conservation of energy says it can not be or
Our primary source of energy is the