This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteria, Subject name: Microbiology
Nocardia is differentiated from Actinomyces by: 
Select and explain. 
A. Gram stain, B. ZN stain, C. Nocardia causes mycetoma, Actinomyces do not, D. Nocardia is facultative anaerobe
B: ZN stain
Answer: B: ZN stain 
Explanation: Ans. is 'b' i.e., Ziehl Neelsen stainRef: (Ananthanarayan, 8th/e, p. 393; 9th/e, p. 394; Harrison, 18th/e, p. 1324; Jawetz, 24th/e, p. 182)Nocardia - Partially acid fast, obligate aerobe, habitat is soil and infections occur exogenously.Actinomyces - Nonacid fast, facultative anaerobe, habitat is oral flora so infections occur endogenously.