Fact 1: Ethologists usually study how animals behave in their natural environment.

Fact 2: Animals behave according to instinct.

Given the two facts above, answer the question "Ethologists study how animals use what in their natural environment" with the following options: 
- Energy
 - Chlorophyll
 - fur
 - digestion
 - instincts
 - lungs
 - an object
 - Energy.


 

     instincts    