user: Question: Who directed an episode that had 2.81 million U.S. viewers?
Columns: ['No. in season', 'No. in series', 'Title', 'Directed by', 'Written by', 'Original air date', 'U.S. viewers (million)']
Types: ['real', 'real', 'text', 'text', 'text', 'text', 'text']
Sample row: [1.0, 82.0, '"Winds of War"', 'John T. Kretchmer', 'Karen Maser', 'March 4, 2012', '3.63']
SQL:

assistant: SELECT "Directed by" FROM "Table" WHERE "U.S. viewers (million)" = '2.81';