在一次TCP连接中，如果某方要关闭连接，则应该发出(1)，这时应答方则应该在收到该报文后，(2)。
A. 在对该报文进行肯定确认后，同时马上发送关闭连接报文
B. 只需对该报文进行肯定确认
C. 在发该报文进行肯定确认后，应该收到应用程序通知后再发送关闭连接报文
D. 需对其做出任何应答
查看答案
甲通过TCP连接给乙发送数据，乙收到序号为500、数据长度为300字节的报文之后，乙将会回复确认号为()的报文给甲。
A. 501
B. 799
C. 800
D. 801
The center function of M-type three-position four-way directional valve is ().
A. pressure port unloading, two working oil ports locking,
B. pressure oil port unloading, two working oil ports unloading
C. all ports are locked
D. all ports are unloaded
In the hydraulic system, which valve can be used as back pressure valve. ()
A. pressure relief valve
B. pressure reducing valve
C. hydraulic control sequence valve
D. speed regulating valve
Low pressure system generally selected __________ structure pressure relief valve as safety valve. ()
A. differential type
B. pilot type
C. direct acting type
D. cone valve type
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