Answer: D. Lou Henry Hoover
First Lady Lou Henry Hoover started the tradition in 1929. Since then, the honor of trimming the state floor Christmas tree has belonged to the nation’s first ladies. First Lady Jacqueline Kennedy is credited with starting the custom of creating a theme for the official White House tree. In 1961, the theme was The Nutcracker Suite. In 2008, after the September 11 attacks, the theme was a "Red, White and Blue Holiday" after many Americans wrote the White House and suggested it. In 2012, First Lady Michelle Obama chose a "Joy to All" theme and trimmed the tree with ornaments decorated by children of military families.