One stage in the lysogeniclife cycle has been shown to cause
dramatic
changes in the phenotype and pathogenicity of bacteria (e. g
makingbacterium
cause botulism). what stage is this?

In the stage of integration of the viral DNA into the host's cell, it is created the prophages. In this interaction, lysogenic conversion may occur, when a prophage induces a change in the phenotype of its host

Explanation:

The lysogenic cycle is a stage of reproduction of some viruses that infect bacteria, inserting their DNA into the bacterial cell. Together with the lytic cycle, they make up the two cycles of viral reproduction.

In the lytic cycle, the genetic material inserted synthesizes RNA that will form the capsids of the new phages and will eventually cause lysis and cell death. In the lysogenic cycle, viral DNA is integrated into the genome of the bacteria. The bacteria will live and reproduce, also replicating viral DNA in new bacteria without the virus manifesting itself. At the moment in which the DNA of the virus separates from the genome of the bacterium, the lytic cycle begins.

In the process of integrating the viral DNA into the bacterial genome, changes in the phenotype of the bacterium, generally associated with its pathogenicity, can occur, to increase the host's survival capabilities, this process is called lysogenic conversion. Even a non-pathogenic bacterium can permanently become pathogenic by lysogenic conversion.

b.

a and c are the answeres