【这句中介词in起什么作用,不可以只用which引到一个定语从句吗?iknewthatevenifthecasewasoneinwhichitwasimpossibletoanticipatetheprobleminadvance,icouldhandlewhateverifound】

　　这句中介词in起什么作用,不可以只用which引到一个定语从句吗?

　　iknewthatevenifthecasewasoneinwhichitwasimpossibletoanticipatetheprobleminadvance,icouldhandlewhateverifound