What is the original airdate of episode #31?
CREATE TABLE "table1_28967275_2" (
  "episode_num" real,
  "series_num" real,
  "episode_title" text,
  "original_air_date" text,
  "production_code" real
);
SELECT "original_air_date" FROM "table1_28967275_2" WHERE "episode_num"=31;