Which Surface has a Round of 4th round, and a Player of maria sharapova?
CREATE TABLE "top_10_wins_per_season" (
  "player" text,
  "ranking" text,
  "event" text,
  "surface" text,
  "round" text,
  "score" text
);
SELECT "surface" FROM "top_10_wins_per_season" WHERE "round"='4th round' AND "player"='maria sharapova';