ci,etNo het mtse asys rpr"osesroc ni hte iskn"
3D fcoleral(lch)eoci mrof uerpxeos of isnk tstar(mu eabas)l ot sun, engisitno fo fs,ih li,mk pn.lsta
D2 errf)(lcglciaoeo mrof enigsinto of atnpl,s gfuni, sae.syt
Both rnetedvco to O-5H2 3D ogra(ets mofr) ni rlvie nad ot hte tvceia fmor O,H1252)-( D3 tli)iclo(rca ni knye.id
The key bit in this question that makes the answer Cholecalciferol rather than 7-dehydrocholesterol is the nugget that the patient "rigorously avoids exposure to the sun." Conversion of 7-dehydrocholesterol to Cholecalciferol can only occur when the skin is exposed to sunlight. Therefore, decreased production of Cholecalciferol (D3) is the better answer.
This picture always helps me remember Vitamin D metabolism.