Enterobacteriacae is classfied based on-

Ans. is 'd' i.e., Lactose fermentation o Initially Enterobacteriacea was classifed on the bases of their lactose fermenting ability on MacConkey's medium, the most popular medium for the isolation of fecal bacilli.o Lactose fermenters produce pink/bright red colonies on MacConkey's agar , while lactose non-fermenters produce pale colonies :Lactose fermenters (rapid) : These are Coliforms, e.g. Escherichia. Klebsiella and Enterobacter aerogenes.Late lactose fermenters (slow) : These are Shigella Sonnei, Serratia, Citrobacter, Arizona, Providencia and Ervinia.Non-lactose fermenters : Shigella except Shigella Sonnei, Salmonella, Proteus.