This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Optics and refraction, Subject name: Ophthalmology
[{'content': 'Soft contact lenses are made of \nSelect and explain. \nA. Polymethyl methacrylate, B. Hydroxymethyl methacrylate, C. Silicone, D. Glass', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Soft contact lenses: Soft contact lenses are made up of HEMA (hydroxyethylmethacrylate) which is hydrophilic. Advantages : Being soft and oxygen permeable, they are most comfoable and so well tolerated. Disadvantages : Problems of proteinaceous deposits, getting cracked, limited life, inferior optical quality, more chances of corneal infections, and inability to correct astigmatism of more than one dioptre. Reference :- A K KHURANA; page:-564', 'role': 'assistant'}]