You are presented with the question "What are used for sensing sound in animals?" and the following answer choices: 
- in the frog family
 - four limbs
 - non-functioning ears
 - noses
 - eyes
 - chemical messengers
 - Electrical energy
 - functioning ears

Now knowing that hearing is used for sensing sound by animals and hearing requires functioning ears, choose the best answer.


 

        functioning ears 