The Mother of a 4-Year-Old Child with Leukemia Says to the Nurse,"I

The mother of a 4-year-old child with leukemia says to the nurse,"I don't understand why he is crying about his legs hurting." The nurse's most informative response would be based on the information that bone pain is related to:

A) elevated WBCs in differential.
B) long periods of inactivity.
C) splenomegaly.
D) bone marrow congested with white cells.