user: Question: Which Surface has an Opponent(s) of Anna-Lena Grönefeld Tatjana Malek?
Columns: ['Year', 'Edition', 'Round', 'Date', 'Location', 'Surface', 'Against', 'Opponent(s)', 'Score', 'Result']
Types: ['real', 'text', 'text', 'text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: [2007.0, 'Group I E/A', 'RR', '19 April', 'Plovdiv', 'Clay', 'Estonia', 'Anett Kaasik Margit Rüütel', '1–6, 6–1, 6–4', '3–0']
SQL:

assistant: SELECT "Surface" FROM "Table" WHERE "Opponent(s)" = 'Anna-Lena Grönefeld Tatjana Malek';