Vibrio cholera evolved virulence through sequential infections by bacteriophage. First, a non$-$pathogenic V$.$ cholera was infected by a bacteriophage that encoded in its genome a pilus gene. This temperate bacteriophage became a prophage. The pilus gene is then expressed causing a pilus structure to be created on V$.$ cholera.

You will recall that normally, upon prophage formation, lysogenic conversion occurs, preventing subsequent infection by new bacteriophage. However, in the case of pathogenic V$.$ cholera, the pilus structure then served as a receptor for the ligand of a second bacteriophage which then infected the bacterium. This second bacteriophage was also temperate and expresses a toxin that causes the severe disease associated with pathogenic V$.$ cholera.

Which three of the following are correct statements?

Temperate bacteriophage do not incorporate their genomes into the bacterial genome.

Lysogenic conversion involves alteration of the outermost sugars and proteins on the cell envelope.

A pilus retracts and can pull a bacteriophage to contact the cell's surface.

V$.$ cholera strains that do not contain the second bacteriophage are probably not pathogenic.