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
A 60-year-old man with a chronic cough, bloody sputum, and marked weight loss is diagnosed as having tuberculosis. A "serpentine-like" colonial morphology is noted on Lowenstein-Jensen agar. This latter finding is caused by which of the following factors? 
Select and explain. 
A. A large "slimy" capsule, B. Wax D, C. Coagulase, D. Cord factor
D: Cord factor
Answer: D: Cord factor 
Explanation: Ans. D. Cord factora. Virulent strains of M. tuberculosis grow in a characteristic "serpentine" cordlike pattern, whereas avirulent strains do not.b. Virulence of the organism is correlated with cord factor (trehalosedimycolate).