Fact 1: Increasing heat causes thermal expansion.

Fact 2: An increase in temperature is the result of the flow of heat into the system.

Given the two facts above, answer the question "he flow of heat into the system causes what?" with the following options: 
- thermal shields
 - thermal detonation
 - thermal expansion
 - Plant growth is reduced
 - chemical reaction
 - Evaporation
 - kinetic energy
 - thermal heat


 

   thermal expansion      