The most reasonable advise would be D. She should rotate often to avoid burning, because first of all, a health provider probably would not recommend or prescribe that your body would not need vitamin d. On the other hand, is known that between 10 a.m. and 4 p.m is the time when the sun is high in the sky, so it would be a very bad advise, and there is no further information as of to know if the person needs supplements instead of sunbathing.