The visiting minister expressed his satisfaction with the talks, ________ that he had enjoyed his stay here.
C
此处所填的词与其后的宾语从句构成状语，表示伴随情景。add是及物动词(有自己的宾语从句)，此处adding表示主动意义，所表示的动作与谓语动作同时发生。
InEurope_______arethetwoleadingcontendersforaglobalreservationssystem.
PoorspeakerofEnglishthoughhewasatthetime,hestillmanagedtomakehimself________.
TheWesternCouncilforTravelResearchin_______employedthetermvisitor.