This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Upper limb, Subject name: Anatomy
[{'content': 'Axillary sheath is derived from \nSelect and explain. \nA. Preveebral fascia, B. Pretracheal fascia, C. Investing layer of deep cervical fascia, D. Deep fascia of throacic wall', 'role': 'user'}, {'content': 'Answer: A \nExplanation: -The muscular floor of the posterior triangle is covered by preveebral layer of fascia colli. -It forms the axillary sheath around subclan aery and brachial plexus travelling from the root of neck to the upper limb. -reference: Textbook of anatomy, Head Neck, and brain, Vishram Singh, 2nd edition, page no.80', 'role': 'assistant'}]