Which Information Obtained by the Nurse Assessing a Patient Admitted

Which information obtained by the nurse assessing a patient admitted with multiple myeloma is most important to report to the health care provider?

A) Serum calcium level is 15 mg/dL.
B) Patient reports no stool for 5 days.
C) Urine sample has Bence-Jones protein.
D) Patient is complaining of severe back pain.