警察伦理学不仅是一门理论科学，规范科学，更是一门实践科学，它把（）作为其研究的出发点和归宿。
参考答案：警察道德实践
圆柱体的侧面展开可以得到一个长方形，这个长方形的长相当于圆柱的______，宽相当于圆柱的______．
Though it was in the midnight, ________ there were a lot of people in the street.
A．and
B．but
C．yet
D．however
