None of them work for me. He is lying in the sand.
Student or Learner
If he were in the water, I'd use b). If I were marking a test, I would accept c) as a possible answer.
You have two b)s in the list - a, b, b and c. I assume it was meant to be a, b, c and d. I wouldn't say he was frolicking. That suggests movement. He is lying in the sand at the moment so I would have to go for "flopping" even though it's not a word I would generally associate with elephants.
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.