have(ali,bac1).
have(reza,bac2).
throat_color(ali,red).
throat_color(bc,black).
stain(bac1,grampos).
stain(bac2,gramneg).
stain(bac3,grampos).
morphology(bac1,coccus).
morphology(bac2,sarcina).
morphology(bac3,coccus).
grow(bac1,chain).
grow(bac2,not_chain).
grow(bac3,chain).
strep_throat(X):-infection(X),
	         streptococcus(Y),
		 have(X,Y).
infection(X):-throat_color(X,red).
streptococcus(X):-stain(X,grampos),
	          morphology(X,coccus),
		  grow(X,chain).