excuse,find,found,go,has,help,is,join,know,learn,let,的单三,现在...答:excuses,excusing,excused;finds,finding,found;founds,founding,founded;goes,going,went;has,having,had;helps,helping,helped;is,being,was;joins,joining,joined;knows,knowing,knew;learns,learning,learned或learnt;lets,letting,let;likes,liking,liked;listens,listening,listened;looks,looking,looked;los...