L3-4椎间盘突出时可能出现的肌力改变是（）
A.伸膝无力
B.趾背伸无力
C.足跖屈无力
D.肛门括约肌无力
E.膀胱括约肌无力
参考答案：A
— Tom has been to Beijing before.
— _______. [ ]
A. So has he
B. So he has
C. So is he
D. So he is
奈曼偏倚是指( )
A．测量偏倚B．入院率偏倚C．诊断怀疑偏倚D．易感性偏倚E．现患-新发病例偏倚
