Dilation occurs when cell walls relax, and conversely, a decrease in light intensity causes dilation of the pupils. Given these facts, what can cause cell walls to relax among the following options:
- Decreased light intensity
 - Something coming from a gland
 - matter vibrating
 - Temperature changing
 - Water vapor cooling
 - the Earth being tilted
 - raising their temperature
 - heat produced


 

 Decreased light intensity        