a te Bl a ckbo a rd in m a in method (yes or not)? • Connection between Bl a ckbo a rd a nd Professor ( a ssoci a tion, a ggreg a tion, composition, re a liz a tion, gener a liz a tion) ? • Connection between Bl a ckbo a rd a nd Student ( a ssoci a tion, a ggreg a tion, composition, re a liz a tion, gener a liz a tion) ? • Connection between Bl a ckbo a rd a nd Cl a ssroom ( a ssoci a tion, a ggreg a tion, composition, re a liz a tion, gener a liz a tion) ? 20