Thank you for the opportunity to help you with your question!
answer is c
This is delayed tanning that takes time to form.
It only happens from exposure to UVB rays! You can’t get it from the UVA in tanning beds. Remember, UVB is the same sun ray that cause sunburn so tanning is part of the continuum of events that culminates in a sunburn.
It begins 2 to 3 days AFTER exposure, becoming maximal at 10 to 14 days (2 weeks!).
It happens WHEN your skin cell’s DNA gets damaged by the UVB so the presence of a tan means DNA has been damaged!
Please let me know if you need any clarification. I'm always happy to answer your questions.