user: Question: How many millions of U.S. viewers watched the episode that first aired on March 31, 2013?
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, 105.0, '"Ashes to Ashes"', 'Kevin Dowling', 'James Stanley', 'March 10, 2013', '2.38']
SQL:

assistant: SELECT "U.S. viewers (million)" FROM "Table" WHERE "Original air date" = 'March 31, 2013';