This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Diseases of orbit, Lids and lacrimal apparatus, Subject name: Ophthalmology
[{'content': 'Meibomian glands secrete which component of sweat- \nSelect and explain. \nA. Water {aqueous}, B. Mucin, C. Protein, D. Lipid', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Oily layer of tear film. Ref khurana 6th edition REF IMG', 'role': 'assistant'}]