user: Question: What is Apparatus, when Rank-Final is greater than 6, and when Competition Description is "U.S. Championships"?
Columns: ['Year', 'Competition Description', 'Location', 'Apparatus', 'Rank-Final']
Types: ['real', 'text', 'text', 'text', 'real']
Sample row: [2008.0, 'U.S. Championships', 'Boston', 'Floor Exercise', 3.0]
SQL:

assistant: SELECT "Apparatus" FROM "Table" WHERE "Rank-Final" > 6.0 AND "Competition Description" = 'U.S. Championships';