This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Head & Neck, Subject name: Anatomy
[{'content': 'Fascia over the posterior triangle is pierced by: \nSelect and explain. \nA. Spinal accessory nerve, B. Suprascapular nerve, C. External jugular vein, D. Internal jugular vein', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. C. External jugular veinExternal jugular veina. Posterior triangle boundariesb. In front- posterior border of sternomastoidc. Behind- Anterior border of trapeziusd. Base- Claviclee. Roof- Skin, superficial fascia, platysma and investing layer of deep cervical fasciaf. Investing layer of deep cervical fascia is pierced by branches of cervical plexus and external jugular veins', 'role': 'assistant'}]