鞭打动作原理
参考答案：
在克服阻力时或身体位移过程中，上肢诸环节依次加速和制动，使末端环节产生极大速度的动作形式。
合成氨工业中，冷交的作用是什么？
A middleman's work may become difficult because ______.
A．manufacturers run their production on a much higher level
B．market demand may not be the same as industrial production
C．retailers are not necessary in running their retailing business
D．retailers demand lower levels than those demanded by manufacturers
