13. When will you make a surgical suggestion as you manage a patient with neck or low back pain? (A) Intractable symptoms for one week (B) No changes in physical findings and no response to conservative management for two weeks (C) Obvious radicular sign without findings of correctable anatomical problem for more than one month (D) No improvement with progressive neurologic deficit in two weeks (E) Mild improvement for more than one month but less than three months