Fact 1: Hearing is used for sensing sound by animals.

Fact 2: Hearing requires functioning ears.

Given the two facts above, answer the question "What are used for sensing sound in animals?" with the following options: 
- in the frog family
 - four limbs
 - non-functioning ears
 - noses
 - eyes
 - chemical messengers
 - Electrical energy
 - functioning ears


 

        functioning ears 