You are presented with the question "What do birds secrete to attract a mate?" and the following answer choices: 
- Energy.
 - Energy
 - fur and fat
 - seeds
 - oxygen
 - pollen
 - Estrogen
 - acetic acid

Now knowing that courtship is behavior that is intended to attract a mate and for example, female birds secrete estrogen in response to the courtship of their male mates, choose the best answer.


 

       Estrogen  