睾丸的生精小管内由管壁到腔面依次有哪些细胞？
参考答案：
精原细胞、初级精母细胞、次级精母细胞、精子细胞、精子。
Jack to _______ China five weeks ago and he ________ back to school tomorrow. [ ]
A. went; was
B. go; come
C. went; will be
D. has gone; will come
电疗法基础知识中，“呈现有规律的脉冲波组的减幅振荡电流”属于（）
A.静电
B.传导电流
C.位移电流
D.介电常数
E.脉冲减幅振荡电流
