On what surface did Katarina Srebotnik play Paola Suárez?
CREATE TABLE "singles_10_4_6" (
  "outcome" text,
  "date" text,
  "tournament" text,
  "surface" text,
  "opponent_in_final" text,
  "score_in_final" text
);
SELECT "surface" FROM "singles_10_4_6" WHERE "opponent_in_final"='paola suárez';