垂向对中装置采用垂向支承，通过调整垂向支承的调节螺栓可以实现车钩端面中心线到（）上表面的距离
A.轨面
B.转向架构架
C.车轮
D.地面
参考答案：A
"不登高山，不知天之高也"属于唯物主义的知行观。( )
For many years, the principle goal of computer (73) was to write short pieces of code that would execute quickly. The (74) needed to be small, because memory was expensive, and it needed to be fast ,because processing power was also expensive.
A．users
B．programmers
C．computer
D．program
