user: Question: What was the court surface on year 1971?
Columns: ['Outcome', 'Year', 'Championship', 'Surface', 'Partner', 'Opponents in the final', 'Score in the final']
Types: ['text', 'real', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Winner', 1968.0, 'French Open', 'Clay', 'Jean-Claude Barclay', 'Billie Jean King Owen Davidson', '6–1, 6–4']
SQL:

assistant: SELECT "Surface" FROM "Table" WHERE "Year" = 1971.0;