This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteriology, Subject name: Microbiology
Corynebacterium diphtheria produce black or grey colonies on the following agar 
Select and explain. 
A. Mac-conkey agar, B. Potassium tellurite agar, C. Thayer main medium, D. Tinsdale agar
B: Potassium tellurite agar
Answer: B: Potassium tellurite agar 
Explanation: 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