user: Question: What person was played against when the playing surface was Hard?
Columns: ['Outcome', 'Date', 'Tournament', 'Surface', 'Partner', 'Opponent', 'Score']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Runner-up', '4 May 2008', 'Marrakech Grand Prix , Fes, Marocco', 'Clay', 'Ekaterina Makarova', 'Sorana Cîrstea Anastasia Pavlyuchenkova', '2–6, 2–6']
SQL:

assistant: SELECT "Opponent" FROM "Table" WHERE "Surface" = 'Hard';