Fact 1: Absorbing sunlight causes objects to heat.

Fact 2: Any object expands when heated and contracts when cooled.

Given the two facts above, answer the question "absorbing sunlight causes objects to" with the following options: 
- Energy.
 - toughness
 - energy
 - warm
 - power
 - expand
 - photons
 - warmth


 

      expand   