Fact 1: Freezing means changing from a liquid into a solid by reducing heat energy.

Fact 2: Liquid water holds a huge amount of heat energy and resists changes of state to solid or gas.

Given the two facts above, answer the question "What turns a liquid into a solid?" with the following options: 
- The bending of a ray of light
 - decreasing liquid
 - reducing heat energy
 - Warm air moving into cold air
 - movement of tectonic plates
 - keeping current temperature
 - adding more heat
 - evaporation


 

   reducing heat energy      