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: Pathology
The "gp 120" in HIV helps in: 
Select and explain. 
A. Virus attachment, B. Virus replication, C. Virus penetration, D. Virus dissemination
A: Virus attachment
Answer: A: Virus attachment 
Explanation: Virus attachment