(A) ** John F. Kennedy
(B) Barrack Obama
(C) Donald Trump
(D) Abraham Lincoln
EXPLANATIONS BELOW
Concept note-1: -The youngest to become president by election was John F. Kennedy, who was inaugurated at age 43. The oldest person to assume the presidency was Joe Biden, the nation’s current president, who was inaugurated at age 78.
Concept note-2: -The biography for President Roosevelt and past presidents is courtesy of the White House Historical Association. With the assassination of President William McKinley, Theodore Roosevelt, not quite 43, became the 26th and youngest President in the Nation’s history (1901-1909).
Concept note-3: -As the second youngest US President, John F Kennedy is followed by Bill Clinton (46 years, 154 days), Ulysses S Grant (46 years, 311 days), Barack Obama (47 years, 169 days), and Grover Cleveland (47 years, 351 days). The oldest president is Joe Biden, who was elected at age 78.