(A) ** 8 years
(B) 1 year
(C) 4 years
(D) 1, 000, 000, 000, 000, 000, 000 years
EXPLANATIONS BELOW
Concept note-1: -Barack Hussein Obama II (/bəˈrɑːk huːˈseɪn oʊˈbɑːmə/ ( listen) bə-RAHK hoo-SAYN oh-BAH-mə; born August 4, 1961) is an American retired politician who served as the 44th president of the United States from 2009 to 2017.
Concept note-2: -Barack Obama’s tenure as the 44th president of the United States began with his first inauguration on January 20, 2009, and ended on January 20, 2017. A Democrat from Illinois, Obama took office following a decisive victory over Republican nominee John McCain in the 2008 presidential election.
Concept note-3: -Jimmy Carter’s retirement, now 42 years, is the longest in American presidential history. At age 98, Carter is also the oldest living president as well as the nation’s longest-lived president.
Concept note-4: -On November 4, 2008, Barack Obama became the first African American to be elected President of the United States, sparking many celebrations in the United States and around the world. He gained almost 53% of the popular vote and 365 electoral votes.