Fact 1: Organisms cluster around hydrothermal vents in the ocean floor.

Fact 2: Hydrothermal vents are powered by the heat of submarine volcanoes.

Given the two facts above, answer the question "Organisms cluster around formations in the ocean floor powered by the heat of submarine what" with the following options: 
- forces
 - volcanoes
 - light energy
 - allow growth
 - thrust
 - waves
 - mines
 - earthquakes


 

  volcanoes       