A65-year-old woman presents with severe mid-back pain of 2 weeks duration. she has no history of trauma. radiographic evaluation reveals compression fractures of t11 and t12. a complete blood count, erythrocyte sedimentation rate, serum protein, serum calcium, phosphate, and parathyroid hormone levels are all within normal ranges. in addition to ordering a dual-energy x-ray absorptiometry (dexa) scan, which of the following laboratory evaluations is most in evaluating this patient for secondary causes of this presentation? (a) bone biopsy(b) rheumatoid factor(c) serum magnesium(d) 25-hydroxyvitamin d(e) antinuclear antibodies test