A 52 year old woman presents to her physician for a check-up. She is recovering from a wrist fracture after a fall. Dual energy x-ray absorptiometry of the hip had shown her to have osteoporosis. She became menopausal at age 50 and did not begin hormone replacement therapy because of a strong family history of breast cancer. She now fears a future hip fracture and would like to begin a bone loss prevention regime.Which of the following pharmaceutical agents is most appropriate for this patient?