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': 'Post-tetanic potentiation is due to - \nSelect and explain. \nA. Hyperpolarization of muscle fibres, B. Rapid K+ efflux, C. Increased availability of Ca++, D. Rapid Na+ influx', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. is \'c\' i.e., Increased availability of Ca++ "Repetitive stimulation enhances force development due to rise in intracellular Ca++, a phenomenon called posttetanic potentiation. It is due to increased phosphorylation of myosine light chain with increased number of cross bridges."', 'role': 'assistant'}]