正常人1次射精量为（）.
A.1～2ml
B.2～3ml
C.3～4ml
D.3～5ml
E.4～5ml
参考答案：D
Follow your teacher's advice, _____ your study will get improved. [ ]
A. or
B. and
C. then
D. so
液压传动装置中的哪两个元件为能量转换装置？
