Final answer:
During viral entry by endocytosis, the host plasma membrane surrounds the entire virion and forms a vesicle, which facilitates the entry of the virus into the host cell.
Step-by-step explanation:
In the process of viral entry by endocytosis, what occurs is that the host plasma membrane completely surrounds the entire virion, which includes the viral nucleic acid and the protein coat. This forms a vesicle around the virion. The correct answer to the student's question is A) The host plasma membrane surrounds the whole virion and forms a vesicle. Additionally, for enveloped viruses, another method of entry into the host cell is fusion, where the viral envelope fuses with the host cell's plasma membrane, but this is distinct from the endocytosis process.