[求助]TK问题?请帮忙解答~~~~~~~~~~~~~~~~

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<P>我又来麻烦了！<IMG src="http://www.spoto.net/bbs/images/Emotions/1.gif"><BR>QUESTION NO: 4<BR>Regarding PAR (Positive Acknowledgement and Re-transmission), which of the<BR>answer choices below are correct? (Select all that apply.)<BR>A. The source device will only retransmit lost packets on the request of<BR>the destination device.<BR>B. The source device starts a timer when it sends a segment and retransmits if<BR>an acknowledgment is not received before the timer expires.<BR>C. The destination device acknowledges receipt of a segment by sending a<BR>packet with a new sequence number and the ACK bit sent.<BR>D. The destination device acknowledges receipt of a segment by sending a<BR>packet that indicates the next sequence number it expects.<BR>E. If the destination device does not receive a segment, all segments<BR>are retransmitted.<BR>F. The source device keeps a record of all segments sent and expects<BR>and acknowledgment of each.<BR>这题该选什么呢<BR>When selecting a Network Interface Card (NIC), which of the following factors need<BR>to be considered? Select three<BR>A. The type of application used on the network<BR>B. The type of system bus used by the computers<BR>C. The type of memory installed in each computer<BR>D. The type of media used in the network topology<BR>E. The type of protocols used in the network<BR>F. The physical layout of the network hosts<BR>还有这题呢？</P>