This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
[{'content': 'This type of tray is used for taking impression of: \nSelect and explain. \nA. Extremely resorbed ridges, B. Restricted mouth opening cases, C. Flabby ridges, D. In patients with severe gag reflex', 'role': 'user'}, {'content': 'Answer: C \nExplanation: This tray is made by using window technique and is used for taking impression of ﬂabby ridges. Flabby tissue is recorded using mucostatic material like low viscosity elastomers.', 'role': 'assistant'}]