This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Body fluid compaments, Subject name: Physiology
[{'content': 'In intracellular fluid, which of the following has least concentration? \nSelect and explain. \nA. Calcium, B. Magnesium, C. Potassium, D. Protein', 'role': 'user'}, {'content': "Answer: A \nExplanation: - Calcium is kept very LOW in cytoplasm, hence intracellular fluid doesn't contain much Ca+2 - Calcium is mostly stored in organelles inside cell - E.g. In sarcoplasmic reticulum of muscle cell etc.", 'role': 'assistant'}]