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': 'Most periodontal fibres are activated when resisting \nSelect and explain. \nA. Torquing forces, B. Horizontal forces, C. Vertical forces, D. Sliding forces', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]