网址：http://m.1010jiajiao.com/timu3_id_2495488[举报]
I didn't know his telephone number．________ it, I ________ then．
If I had known; would have rung him up
Should I know; would have rung him up
If I knew; would ring him up
Had I known; would ring him up
I didn’t know his telephone number．_________ it, I _________ then．
Had I known, would ring him up
Should I know, would have rung him up
Had I known; would have rung him up