You are answering a USMLE-style medical question. Question: A 48-year-old woman comes to the physician because of intermittent pain in her neck, right shoulder, and arm, as well as a tingling sensation in her right hand. She first noticed her symptoms after she got off a rollercoaster ride 2 months ago. Physical examination shows weakness when extending the right wrist against resistance. An MRI of the head and neck is shown. This patient's condition is most likely the result of nerve root compression by a structure derived from which of the following embryologic layers? Options: A) Neural crest B) Notochord C) Neural tube D) Surface ectoderm Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.