Fact 1: Ultraviolet light causes sunburn.

Fact 2: Sunburns are painful and can be dangerous.

Given the two facts above, answer the question "What can be dangerous?" with the following options: 
- Pesticides
 - friendship
 - Ultraviolet light
 - love
 - influenza
 - killing insects
 - if humans disturb bears
 - progression


 

   Ultraviolet light      