<prompt> An 11-year-old boy falls down the stairs. A physician examines a radiograph of the boys shoulder region. If the structure indicated by the letter B is fractured, which of the following structures is most likely injured?Musculocutaneous nerveRadial nerveDeep brachial arteryPosterior humeral circumflex artery  <response>: d Fracture of the surgical neck of the humerus occurs commonly and damages the axillary nerve and the posterior humeral circumflex artery. 