How do bacteria cause disease?
a. a bacterium injects its dna into the genome of a host cell.
b. a bacterium reproduces inside a host cell and causes the cell to
break open.
c. a bacterium replaces the host cells with bacterial cells.
d. a bacterium releases harmful proteins or other poisons into the
host's body

A Bacterium injects its DNA into the genome of the host cel. (Ans. A)

Explanation:

This stage of bacteria causing disease is known as Lytic cycle ,in this cycle phage 1st binds to the receptor present on the surface of the bacterial cell. Then the phage injects its DNA into the host cell and then protein synthesis and DNA coping occurs. The capsid proteins are stuffed with DNA to make lots of new phages particles.