The correct answer is: The acting president may retain office for a maximum of 10 years as long as there are more than two years left in the previous president’s term.
According to the 22nd Amendment of the U.S. Constitution, if a Vice President assumes the presidency, they can serve for up to two additional terms, but if they serve more than two years of the former president's term, those years count against the two-term limit. Therefore, they can only serve a total of 10 years maximum if they took over a presidency with more than two years remaining.