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
Confirmatory tests for Corynebacterium diphtheriae is 
Select and explain. 
A. Serological tests, B. Isolation in selective media, C. Test for toxin, D. None of the above
B: Isolation in selective media
Answer: B: Isolation in selective media 
Explanation: Selective media for Corynebacterium diphtheriae is Tellurite blood agar. Several modifications of Tellurite blood agar have been utilized, such as McLeod's and Hoyle's medium. Tellurite inhibits the growth of most of the other bacteria acting as a selective agent for diphtheria bacilli. Diphtheria bacilli reduce Tellurite to metallic tellurium which is incorporated in the colonies giving them a grey or black colour. Reference: Textbook of Microbiology; Anathanarayan and panicker's; 10th edition; Page no: 242