This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: general microbiology, Subject name: Microbiology
Gram stain is a? 
Select and explain. 
A. Simple stain, B. Differential stain, C. Negative stain, D. Fluorescent stain
B: Differential stain
Answer: B: Differential stain 
Explanation: The Gram stain is the most impoant staining procedure in microbiology. It is used to differentiate between gram positive organisms and gram negative organisms. Hence, it is a differential stain. Gram negative and gram positive organisms are distinguished from each other by differences in their cell walls. Ref: Ananthanarayana & panikers 9th edition