Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Outcome | Year | Championship | Surface | Partner | Opponents in the final | Score in the final |
| --- | --- | --- | --- | --- | --- | --- |
| Winner | 1968.0 | French Open | Clay | Jean-Claude Barclay | Billie Jean King Owen Davidson | 6–1, 6–4 |
| Runner-up | 1969.0 | French Open | Clay | Jean-Claude Barclay | Margaret Court Marty Riessen | 6–3, 6–2 |
| Runner-up | 1969.0 | US Open | Grass | Dennis Ralston | Margaret Court Marty Riessen | 6–4, 7–5 |
| Runner-up | 1970.0 | French Open | Clay | Jean-Claude Barclay | Billie Jean King Bob Hewitt | 3–6, 6–4, 6–2 |
| Winner | 1971.0 | French Open | Clay | Jean-Claude Barclay | Winnie Shaw Thomas Lejus | 6–2, 6–4 |
| Runner-up | 1972.0 | French Open | Clay | Jean-Claude Barclay | Evonne Goolagong Cawley Kim Warwick | 6–2, 6–4 |
| Winner | 1973.0 | French Open | Clay | Jean-Claude Barclay | Betty Stöve Patrice Dominguez | 6–1, 6–4 |
Question:
What was the court surface on year 1971?
Answer:
Clay