Fact 1: Dilation occurs when cell walls relax.

Fact 2: Animals have no cell walls.

Given the two facts above, answer the question "Dilation occurs when part of a cell that a what does not have relaxes." with the following options: 
- breathing
 - organ
 - the eyes
 - abrasion
 - complex
 - animal
 - nerves
 - retina


 

      animal   