CREATE TABLE "singles_5" (
  "date" text,
  "tournament" text,
  "surface" text,
  "opponent_in_the_final" text,
  "score" text
);

Question: Who was the finals opponent on the hard surface tournament?
SQL: SELECT "opponent_in_the_final" FROM "singles_5" WHERE "surface"='hard';

Question: Which surface was played during Curitiba tournament?
SQL: SELECT "surface" FROM "singles_5" WHERE "tournament"='curitiba';