Have you ever been to Shanghai?---Yes. I ________ there a few months ago.
A have been
B. went
C. have gone
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When I returned home, I found I _____my umbrella in the office.
A. will leave
B. was leaving
C. have left
D. had left
I ______many friends since I came here.
A. make
B. am making
C. made
D. have made
--I don't know if Mr.Li______ to the party this evening.--I think he will come if he ____free.
A. will come; is
B. will come; will be
C. comes;is
D. comes; will be
下列对DR和BDR说法正确的是()?
A. BDR优先于DR
B. 在选举DR的同时也会选举BDR
C. 优先级最高的被选举BDR,优先级次高的被选举为DR
D. 当DR/BDR已经选举完毕,就算一台具有更改优先级的路由器变为有效也会替换该网段中已经选举的DR/BDR成为新的DR/BDR
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