Fact 1: Insulated material can be used for keeping warm.

Fact 2: Birds waste a lot of body heat trying to keep warm in exposed areas.

Given the two facts above, answer the question "insulated material can be used to prevent wasting a lot of what?" with the following options: 
- sunny days
 - body heat
 - body water
 - heat energy
 - contained areas
 - electricity
 - fever sweats
 - power


 

  body heat       