Which three statements about end-to-end delay are true？ （） [" End-to-end delay is the sum of propagation delays， processing delays， serialization delays， and queuing delays."," Coast-to-coast end-to-end delay over an optical link is about 20 ms."," Processing delay depends on various factors， which include CPU speed， CPU utilization， IP switching mode， and router architecture."," Propagation and serialization delays are related to the media."," Propagation delay is the time it takes to transmit a packet and is measured in bits-per-second （bps）."," Serialization delay is the time it takes for a router to take the packet from an input interface and put it into the output queue of the output interface."]
气剂301用于焊接（）。 ["铝及铝合金","铜及铜合金","不锈钢","铸铁"]
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流感的特点是全身中毒症状较轻，发热与上呼吸道症状较重。
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