第23题:[多选题]GGSN中,离线计费可分为()。
In GGSN,the offline charging is classified into (). A.普通离线计费(按时间)
Normal offline charging(by time) B.普通离线计费(按流量)
Normal offline charging(by traffic) C.离线内容计费
Offline content based charging D.热计费
Hot Charging 参考答案:ABCD
第33题: [单项选择]John said that he _______ London twice. A. have been to B. have gone to C. had gone to D. had been to 参考答案:D 答案解析:宾语从句。约翰说他去过伦敦两次。▲宾语从句的时态要和主句保持一致。本题因为主语为一般过去时,所以从句要用过去完成时态,A,B不正确。C表示“到伦敦去了(还没有回来)”,与题意不符。