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: Physiology
[{'content': 'The force of muscle contraction can be increased by all of the following except \nSelect and explain. \nA. Increasing the frequency of activation of motor units, B. Increasing the number of motor units activated, C. Increasing the amplitude of action potentials in the motor neurons, D. Recruiting larger motor units', 'role': 'user'}, {'content': 'Answer: C \nExplanation: The amplitude of action potential cannot be increased as it follows ‘All or none’ law. Force of contraction can be increased by increasing the number of motor units involved in contraction, by increasing the frequency of activation of motor units or by recruiting larger motor units.', 'role': 'assistant'}]