Answer: Option D
Explanation: We must complete the sentence:
Voy a la playa para ________ el sol.
In the Spanish sentence, the idea transmitted is that the person talking want to go to the beach to take a sunbath (looking at the options this is the one that makes sense)
if you want to say "I am going to take a sunbath" in Spanish, you should say "Voy a Tomar el sol" so the option that completes the sentence is D.
Voy a la playa para Tomar el sol.