Explanation:

- Option 1, Rafael Nadal: Nadal won the French Open in 2020, securing his 13th title there, but he did not win the ATP Finals.

- Option 2, Daniil Medvedev: Medvedev won the ATP Finals in 2020, defeating Dominic Thiem in the final.

- Option 3, Roger Federer: Federer did not win any major ATP tournaments in 2020 as he was recovering from surgery.

- Option 4, Novak Djokovic: Djokovic ended the year ranked number one but did not win the ATP Finals.

- Option 5, None of the above/More than one of the above: Not applicable as only Medvedev won the ATP Finals in 2020.