Detailed Instructions: Given a scientific passage and an answer, generate a question for the given answer.
Q: Passage: Skeletal system problems include osteoporosis, bone fractures, and ligament sprains. A diet rick in calcium and vitamin D may reduce the risk of osteoporosis and related bone fractures. Following safe practices may also reduce the risk of fractures as well as sprains. Answer: vitamin d
A:
A diet rich in calcium and what vitamin may reduce the risk of osteoporosis and related bone fractures?