Is authentication of documents mandatory to use in china and requiements of study visa,etc.

My G.daughter is going to study MBBS 6 years course in a university in china.She has to get study X type from china consulate New York.What is requirement to get china student X type.Secondly.someone told me that documents must be authenticated.Authenticated documents are necessary to use in china.who will authenticate and what documents needed to be authenticate?.What documents needed at the time of registration in university.She is US citizen and she got high school diploma from a school in newyork.Please advise.thanksother details