肝脏的含液性病变在声像图上表现为:Ⅰ-边界清晰Ⅱ-内部呈无回声或有细弱光点Ⅲ-其后壁和后方回声呈增强效应()
A.Ⅰ,Ⅱ
B.Ⅱ
C.Ⅰ,Ⅲ
D.Ⅰ
E.Ⅰ,Ⅱ,Ⅲ
参考答案:E
试述费孝通《乡土中国》的基本内容。
You keep the book for a week. [ ]
A. can
B. have to
C. must
D. should