Ultraviolet light causes sunburn, and sunburns cause the skin to become red and painful to the touch. Given these facts, what causes skin to become red and painful to the touch among the following options:
- skin lotion
 - chemical messengers
 - lightening creams
 - chemical reaction
 - ultraviolet light
 - lightening skin
 - sensory neurons
 - deoxyribonucleic acid


 

     ultraviolet light    