user: Question: Who were the opponents that played on a Hard surface on July 13, 2008?
Columns: ['Date', 'Tournament', 'Surface', 'Partner', 'Opponents', 'Score']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['July 13, 2008', 'Granby , Canada', 'Hard', 'Philip Bester', 'Alberto Francis Nicholas Monroe', '2–6, 6–1, [10–5]']
SQL:

assistant: SELECT "Opponents" FROM "Table" WHERE "Surface" = 'Hard' AND "Date" = 'July 13, 2008';