参考以下拓扑及配置，路由器R1与R2通过Serial低速线缆连接，且数据链路层使用PPP。当R1和R2的Holdtime不一致时，ARP协商失败，无法通信。
–Brand was Jane 's brother!
–()he reminded me so much of Jane!
A. No wonder
B. No doubt
C. Above all
–Is your grandmother getting well now？
–()
A. She gets up early and do exercise every day.
B. Yes, she is much better now. Thank you.
C. I don 't believe that she feels comfortable.
–OK, I 'll fix your computer right now.
–Oh, take your time.()
A. I can 't stand it.
B. I'm in no hurry.
C. That 's a great idea.
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