user: Question: When Bas van Erp was the athlete what was the quarterfinals?
Columns: ['Athlete', 'Class', 'Event', 'Round of 64', 'Round of 32', 'Round of 16', 'Quarterfinals', 'Semifinals', 'Final/ Bronze medal match']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Robin Ammerlaan', 'Open', 'Singles', 'Reid ( GBR ) W 6-3, 6-0', 'Rajakaruna ( SRI ) W 6-0, 6-0', 'Welch ( GBR ) W 6-2, 6-3', 'Saida ( JPN ) W 6-4, 6-2', 'Vink ( NED ) W 7-5, 4-6, 7-6(6)', 'Kunieda ( JPN ) L 3-6, 0-6']
SQL:

assistant: SELECT "Quarterfinals" FROM "Table" WHERE "Athlete" = 'Bas van Erp';