Which pre-season has May 5 of 21?
CREATE TABLE "ranking_movement" (
  "poll" text,
  "pre_season" text,
  "mar_3" text,
  "may_5" text,
  "may_12" text,
  "may_19" text,
  "may_26" text,
  "final_poll" text
);
SELECT "pre_season" FROM "ranking_movement" WHERE "may_5"='21';