Viral DNA that has become integrated into the chromosome of a bacterium is called a

Explanation

Prophage is the term reserved for phage DNA sitting integrated and inactive in a bacterial chromosome. Provirus describes the same situation in an animal cell, as with HIV DNA in a human T lymphocyte, so it is the tempting wrong answer here because the host is bacterial. A prion is an infectious protein and a viroid is a naked infectious RNA, neither of which integrates in this way.