The labeled viral structure in the diagram above stores viral DNA in the head (number 4) similarly to the way the nucleus stores cellular DNA.
A virus is a term to refer to a microscopic particle characterized by infectious genetic information (DNA) that reproduces once it infects the host's cells. The image shows the structure of a complex virus, it has the following parts:
Head (number 4)
Collar (number 3)
Tail (number 2)
Long-Tail fiber (number 1)
In the head, it stores the genetic information that is later transmitted to the cells of the host it infects. Likewise, it uses its cells to multiply. So the correct answer is 4.