Complex sentence: She is also the only person to have indisputably lived for 120 years, the closest person to reach this age was Sarah Knauss of the United States, reaching 119 years, 97 days on her death on 30 December 1999.
Split into simpler sentences: She is also the only person to have indisputably lived for 120 years. The person who came closest to this age was Sarah Knauss of the United States, reaching 119 years, 97 days on her death on 30 December 1999.