Methods: the breakfast structure and the nutrition knowledge of 3 547 students in rural boarding middle school in Chongqing were investigated by adopting stratified two-stage cluster sampling method.
方法：采用分层二阶段整群抽样方法，对重庆市3 547名中学生早餐饮食结构和营养知识进行调查。
Methods: the breakfast structure and the nutrition knowledge of 3 547 students in rural boarding middle school in Chongqing were investigated by adopting stratified two-stage cluster sampling method.
方法：采用分层二阶段整群抽样方法，对重庆市3 547名中学生早餐饮食结构和营养知识进行调查。
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