卫生费用研究的主要对象是______的卫生费用。

Mrs. Cray, an African American, is admitted to the hospital after sustaining a hip fracture. She is 5 ft. , 4 inches tall and weighs 96 lbs. She has five children and has used estrogen replacement therapies for 10 years. She told the nurse that she "just stepped forward and fell. " The results of her bone density tests indicate she has osteoporosis. Which of the following is the greatest risk factor for osteoporosis for this woman

A. Her long-term use of estrogen.
B. Her weight.
C. Her family.
D. Her rac