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 difference between gram + ve and gram -ve organism is that Gram +ve org. contains - 
Select and explain. 
A. Teichoic acid, B. Muramic acid, C. N-Acetylneuraminic acid, D. Aromatic amino acids
A: Teichoic acid
Answer: A: Teichoic acid 
Explanation: Comparison of cell walls of Gram-positive and Gram-negative bacteria