土地是重要的生产资料，尤其是在生产力还不发达的古代社会，统治者更是十分重视土地问题的解决。商鞅变法、北魏孝文帝改革、俄国农奴制改革是如何解决土地问题的？这一问题的解决分别产生了什么影响？

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女患，51岁，右肩及上肢痛7个月。查体：右肩以下感觉消失，上肢肌张力减低，肱二头肌、三头肌反射（+），下肢肌张力增高，腱反射（++++），双侧Babinski征（+）。（）

A.延髓

B.颈髓

C.胸髓

D.腰髓