CREATE TABLE table_38573 ("Date" CLOB, "Tournament" CLOB, "Surface" CLOB, "Opponent" CLOB, "Score" CLOB)

WHich Surface has an Opponent of gustavo kuerten?
SELECT "Surface" FROM table_38573 WHERE "Opponent" = 'gustavo kuerten'
SELECT "Surface" FROM "table_38573" WHERE "Opponent" = 'gustavo kuerten'