Which of the following processes would a virus most likely use to attach to a host cell?

Viruses typically attach to host cells through a method known as receptor-mediated endocytosis. This process involves the virus binding to specific receptors on the surface of the host cell. These receptors are usually proteins specific to the host’s cellular functions, and the virus exploits these to gain entry.

Once the virus attaches to the receptor, the host cell's membrane can internalize the virus, allowing it to enter the cytoplasm. This method is efficient for viruses, as it takes advantage of the cellular machinery and processes that already exist, ensuring a higher likelihood of successful entry.

Other processes, such as direct penetration, involve different mechanisms that are not typical for most viruses, which often have a protective protein coat that needs to be bypassed. Additionally, nucleophilic attack refers to a chemical reaction mechanism not relevant to viral entry, while facilitated diffusion pertains to the transport of molecules across membranes without the need for energy, making it unsuitable for explaining viral attachment and entry.