You are presented with the question "Why do the flightless have feathers?" and the following answer choices: 
- layers of fat
 - Sublimation
 - it needs them
 - warm-blooded
 - Air conditioning
 - Radiation
 - Insulation
 - protect them

Now knowing that feathers help birds fly and provide insulation and some birds are flightless birds, choose the best answer.


 

       Insulation  