This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
Which of the following organism requires tryptophan for growth - 
Select and explain. 
A. H. influenza, B. Vibrio, C. Gonococci, D. Salmonella typhi
D: Salmonella typhi
Answer: D: Salmonella typhi 
Explanation: Ans. is 'd' i.e., Salmonella typhi