Which structure allows a virus to recognize and attach to receptors on the host cell? a. cell wall
b. capsid protein
c. cell membrane
d. nucleic acid

All viruses contain a nucleic acid genome and a protein capsid that covers the genome.

The capsid protein is the structure that allows a virus to recognize and attach to receptors on the host cell.  Correct B This protein shell of a virus provides proteins that enable the virion to penetrate the host cell membrane and, in some cases to inject the infectious nucleic acid into the cell's cytoplasm.