Corynebacterium diphtheria produce black or grey colonies on the following agar: (A) Mac-conkey agar, (B) Potassium tellurite agar, (C) Thayer main medium, (D) Tinsdale agar
Answer is B. Corynebacterium produce black or grey colonies on potassium tellurite blood agar It acts as a selective medium for its growth Ref: Textbook of Microbiology Baveja 5th ed Pg 211