Final answer:
Exposure to intercalating agents is the mutagen that might increase the incidence of slipped-strand mispairing, leading to insertions or deletions and potentially causing frameshift mutations.
Step-by-step explanation:
The mutagen that might increase the incidence of slipped-strand mispairing is D. exposure to intercalating agents. Intercalating agents, such as acridine and ethidium bromide, are chemicals that insert themselves between the base pairs in the DNA double helix. This can cause the DNA polymerase to introduce insertions or deletions during DNA replication, potentially leading to frameshift mutations. These mutations may result in serious consequences, including the disruption of gene function and the potential development of cancer.