This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Morphology and Physiology of Bacteria, Subject name: Microbiology
Gram Stain is a: 
Select and explain. 
A. Simple stain, B. Differential stain, C. Negative stain, D. None
B: Differential stain
Answer: B: Differential stain 
Explanation: Ans. (b) Differential stainRef.: Microbiology by Ananth and Paniker 8th ed./15DIFFERENTIAL STAIN* These are positive stain, which divide bacterial population into two different groups by imparting two different colors# Gram Stain: it is the most common staining method of bacteriology. It stains cell wall of bacteria. Gram positive appears blue Gram Negative appears pink/red# Z-N stain is used to distinguish acid fast bacteria and non-acid fast bacteria. Presence of mycolic acid is responsible for the acid-fast nature of bacteria.