user: Question: What is the surface when the US Open is the championship in the year 1979?
Columns: ['Outcome', 'Year', 'Championship', 'Surface', 'Partner', 'Opponents', 'Score']
Types: ['text', 'real', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Winner', 1975.0, 'French Open', 'Clay', 'Chris Evert', 'Julie Anthony Olga Morozova', '6–3, 6–2']
SQL:

assistant: SELECT "Surface" FROM "Table" WHERE "Championship" = 'US Open' AND "Year" = 1979.0;