This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Virology, Subject name: Microbiology
Which is the longest DNA of hepatitis B virus- 
Select and explain. 
A. P gene, B. X gene, C. S gene, D. C gene
A: P gene
Answer: A: P gene 
Explanation: The p gene is the largest and codes for the DNA polymerase enzyme. REF:ANATHANARAYAN AND PANIKER'S TEXTBOOK OF MICROBIOLOGY 9TH EDITION PAGE NO:544