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人们饮用牛奶已有好几千年的历史,牛奶的营养成分现在已被大家普遍认识。然而并不是所有人都能有福气享用牛奶。这是为什么呢?
People have been drinking milk for thousands of years and the nutritional content of milk is now widely recognized. However, not all people have the blessing to enjoy milk. Why is this?