Many animal viruses have proteins called ______ that attach to receptors on host cells.

• A. spikes
• B. envelopes
• C. nucleocapsids
• D. capsomeres

Answer: (A)

Verified step by step guidance

1. Understand the structure of animal viruses: they often have an outer layer called an envelope, which can contain specific proteins.
2. Recognize that these proteins are responsible for attaching the virus to the host cell by binding to receptors on the cell surface.
3. Recall the terminology used for these attachment proteins; they are commonly referred to as 'spikes' because they protrude from the viral envelope.
4. Differentiate 'spikes' from other viral components: 'envelopes' are the lipid layers, 'nucleocapsids' are the protein shells around the viral genome, and 'capsomeres' are the protein subunits of the capsid.
5. Conclude that the correct term for the proteins that attach to host cell receptors is 'spikes'.