In which step of the diagram is the provirus formed

Step B

Explanation:

Provirus refers to the genome of virus that is integrated into the genome of the host cell. The infection cycle of virus starts with attachment of virus to the host cell followed by entry of viral genome into the host cell.  Once inside the host cell, the viral genome become integrated into the host genome and is replicated along with it. In given image, step B shows the provirus since viral genome has been integrated with genome of host cell.