逐级签订安全目标责任状是为了：层层分解安全指标，明确每个岗位、部门、人员应负的安全责任。
参考答案：对
A．Because it did not shoot far.
B．Because it did not bend easily.
C．Because it was too heavy.
D．Because its string was short.
曲柄滑块机构中曲柄转速为6r/min，则滑块一个往复行程的时间是（）
A.1s
B.6s
C.10s
D.60s
