The correct answer is letter C. Air is the only element that Karra has not mastered by the first episode of The Legend of Korra. It is an American animated series created by Michael Dante DiMartino and Bryan Konietzko which aired on Nickelodeon from April 14, 2012 to December 19, 2014 wherein Korra is the main character. The series has a total of four seasons – Season 1 was entitled Book One:
Air, Season 2 was entitled Book Two Spirits, Season 3 was entitled Book Three: Change and Season 4 was entitled Book Four: Balance. During the first episode of the first season, it was shown that Korra has mastered three out of the four bending elements – Earth, Water and Fire – and she sought Tenzin’s help to teach her how to bend the air.