user: Question: Who was the opponent on 19 February 2011?
Columns: ['Outcome', 'Date', 'Surface', 'Opponent', 'Score']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['Winner', '14 June 2009', 'Grass', 'Li Na', '6–0, 7–6 (7–2)']
SQL:

assistant: SELECT "Opponent" FROM "Table" WHERE "Date" = '19 February 2011';