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: Action potential follows an all or none law. When sufficient amplitude is reached to produce a motor response, increasing the amplitude fuher will not have any effect on the motor response. Ref: Review of Medical Physiology by William F Ganong, 19th Edition Page 70 ; Biomechanics and Biology of Movement By Benno Maurus Nig, Page 275.', 'role': 'assistant'}]