A60-year-old woman fell down the stairs with severe left arm pain. Onexamination, the woman was unable to extend the wrist and fingers,and the wrist was flexed. The skin sensation of the back of the armand forearm was also lost, which of the following nerves may beinjured?() A: axillarynerve B: musculocutaneousnerve C: ulnarnerve D: mediannerve E: radialnerve