Test center: Main nutrients needed by human body: Analysis: Food contains six nutrients such as protein, sugar, fat, vitamins, inorganic salts and water, and each nutrient has a certain function. Once lacking, it will lead to corresponding diseases. A anemia is caused by iron deficiency or protein deficiency, and rickets is caused by calcium deficiency or vitamin D deficiency. A mistake. B, osteoporosis and rickets are caused by calcium deficiency or vitamin D deficiency, B right. C, scurvy is caused by vitamin C deficiency, vitamin B 1 deficiency is prone to beriberi, C error. D, anemia is caused by iron deficiency or protein deficiency; Scurvy is due to lack of vitamin C, and D is wrong. Therefore, the key to answering this question is to master the causes of common diseases skillfully and answer questions flexibly in combination with the meaning of the questions.