关于Ms/phd 和Phd 这两个degree的选择问题

申请cornell 和CMU 在degree的选项中都出现了 这个选择
这两个degree的区别是不是就是本科还是硕士直接申 phd的区别呢 本科要选ms/phd 硕士要选择phd
尤其在cornell官网上发现有这么一句话[size=13.333333969116211px]Those applying for direct admission to the PhD program are expected to have a master's degree in an appropriate area first; otherwise, they should apply to the combined M.S./Ph.D. program.。。。而且网上其他被录取了ms/phd的还要自费    这也太坑爹了吧。。。。。。。。
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同时在cmu的官网上没有发现 这个degree的介绍。。。而且 phd requirments 里面写着After completion of the M.S. degree at Carnegie Mellon or elsewhere, students are eligible for admission as candidates for the Ph.D. degree. Typically, at least four years of graduate study beyond the B.S. degree or three years of graduate study beyond the M.S. degree are required.。。。。。这到底是允不允许本科生申请嘛。。。
求解答

可以申请，cmu的你申phd如果没录上会考虑给你ms ad，至少cs是这样的