20．He said he would accept the job, so we have asked him to __________ his acceptance in writing．

　　　　 A．confirm　 　　　　　　 B．prove　 　　　　　　　　 C．sign　 　　　　　　　　　　 D．announce

19．When she was in trouble, I did what I could to help her．__________ my help, she wrote me a letter of thanks．

　　　　 A．In honor of　 　　　 B．In case of　 　　　　　 C．In terms of　 　　　 D．In return for

18．With the evening drawing near, the guide __________ tourists and took them to the hotel．

　　　　 A．rounded up　 　　　 B．made up　 　　　　　　　 C．fed up　 　　　　　　　　　 D．put up