You are presented with the question "What causes skin to become red and painful to the touch?" and the following answer choices: 
- skin lotion
 - chemical messengers
 - lightening creams
 - chemical reaction
 - ultraviolet light
 - lightening skin
 - sensory neurons
 - deoxyribonucleic acid

Now knowing that ultraviolet light causes sunburn and sunburns cause the skin to become red and painful to the touch, choose the best answer.


 

     ultraviolet light    