系统误差的性质特点是（）。
A．随机产生
B．具在单向性
C．呈正态分布
D．难以测定
参考答案：B
---You seemed to have been impressed by his songs.
---Well, not exactly so. It was his way of singing____ his voice that really impressed me.
A．rather than
B．as well as
C．but also
D．together with
油气集输系统的功能是什么？
