单选题：Questionsare based on the following passage.Older women who

Questionsare based on the following passage.
Older women who take vitamin D and calcium supplements to prevent broken bones may be taking them in vain, according to leading experts. A U.S. government advisory group found taking typical low doses provided no benefits for average postmenopausal(绝经后的)women.
What is more taking 4OOIU of vitamin D and 1,000mg of calcium daily increased the risk of developing kidney stones. Both nutrients are crucial for building and maintaining strong, healthy bones and specialists advise getting as much as possible from a good diet and exposure to sunlight. If an older person has a vitamin deficiency or bone-thinning osteoporosis (骨质疏松症), doctors often prescribe higher- than-normal doses. But for otherwise healthy post-menopausal women, adding modest supplements to their diet makes no impact.
It isn't clear if those doses offer bone protection if taken before menopause, or if they help men's
bones, according to the new guidelines from the U.S. Preventive Services Task Force.
It's a confusing message considering that for years, calcium and vitamin D supplements have been widely considered an insurance policy against osteoporosis, with little down-side to taking them. The NHS currently recommends people over 65 take a dally vitamin D pill, although no more than 25 micrograms.
"Regrettably, we don't have as much information as we would like to have about a substance that has been around a long time and we used to think we understood," said Dr. Virginia Moyer of the Baylor College of Medicine, who heads the task force. "Turns out, there's a lot more to learn. " The recommendations are not for people at high risk of weak bones, such as those with a history of bone fractures. These people should consult their local doctor. In the U.S. the average adult is advised to get about 1,000rag of calcium, 1 ,300 for post-menopausal women, every day. For vitamin D, the goal is 600 IUs ofvitamin D daily moving to 800 after age 70. The nutrients can be found in foods including orange juice fortified with calcium: dairy foods such as milk, yogurt and cheese; certain fish including salmon; and fortified breakfast cereals.
It can be learned that taking low doses of vitamin D and calcium supplements will________ to aver- age post-menopausal women. A．be beneficial
B．bring harm
C．make no difference
D．increase the risk of developing kidney stones