Question

the viral structure responsible for recognizing specific host cells is - a bacteriophage. genetic material. a retrovirus. a surface protein.

Explanation:

Viruses use surface proteins to recognize and bind to specific host cells. Bacteriophages are viruses that infect bacteria, genetic material (DNA/RNA) carries the virus's genetic information, and retroviruses are a type of virus with RNA as genetic material that uses reverse - transcriptase. But the structure for host - cell recognition is the surface protein.

Answer:

a surface protein.