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
The method used for acid-fast staining - 
Select and explain. 
A. Robertson’s method, B. Ziehl Neelsen, C. Silver impregnation method, D. Dark ground illumination
B: Ziehl Neelsen
Answer: B: Ziehl Neelsen 
Explanation: Acid-fast staining

After staining with aniline dye, acid-fast organisms resist decolourisation with acids.
The method most commonly used is modified Ziehl Neelsen.