在平车场下放时，不要松绳过多，以避免车辆在突然下坡时造成对钢丝绳的冲击破坏。
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加快资本周转，可以增加年剩余价值量和提高年剩余价值率，根本是因为（）
A. 剩余价值率提高了
B. 预付可变资本发挥的作用增加了
C. 流通对生产的反作用
D. 预付的资本总量增加了
制备含有共熔成分散剂时，可将共熔成分先共熔，再以其他成分吸收，使其分散均匀。
A. 正确
B. 错误
Regarding PAR (Positive Acknowledgement and Re-transmission), which of the answer choices below are correct?（）
A. The source device will only retransmit lost packets on the request of the destination device.
B. The source device starts a timer when it sends a segment and retransmits if an acknowledgment is not received before the timer expires.
C. The destination device acknowledges receipt of a segment by sending a packet with a new sequence number and the ACK bit sent.
D. The destination device acknowledges receipt of a segment by sending a packet that indicates the next sequence number it expects.
E. If the destination device does not receive a segment, all segments are retransmitted.
F. The source device keeps a record of all segments sent and expects and acknowledgment of each.
预测煤层突出危险性的单项指标值中，煤的坚固性系数f≤（）时，煤层有突出危险性。
A. 0.5
B. 1.0
C. 1.5
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