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 | Date | Tournament | Surface | Opponent | Score |
| --- | --- | --- | --- | --- | --- |
| Runner-up | 12 November 2007 | Helsinki , Finland | Hard (i) | Steve Darcis | 3–6, 6–1, 4–6 |
| Runner-up | 26 May 2008 | Karlsruhe , Germany | Clay | Teymuraz Gabashvili | 1–6, 4–6 |
| Runner-up | 12 April 2010 | Baton Rouge , US | Hard (i) | Kevin Anderson | 7–6 (9–7) , 6–7 (7–9) , 1–6 |
| Runner-up | 31 May 2010 | Fürth , Germany | Clay | Robin Haase | 4–6, 2–6 |
| Winner | 26 July 2010 | Granby , Canada | Hard | Milos Raonic | 6–3, 7–6 (7–4) |
| Winner | 11 October 2010 | Tiburon , US | Hard | Ryan Harrison | 6–1, 6–1 |
| Winner | 13 November 2011 | Loughborough , UK | Hard | Flavio Cipolla | 6–2, 7–5 |
| Runner-up | 7 July 2012 | Braunschweig , Germany | Clay | Thomaz Bellucci | 6–7 (4–7) , 3–6 |
| Winner | 16 September 2012 | Pétange , Luxembourg | Hard | Paul-Henri Mathieu | 7–6 (9–7) , 6–4 |
Question:
The game played 31 May 2010 was played on what surface?
Answer:
Clay