Which Reason has a State (class) of tennessee (2)?
CREATE TABLE "senate" (
  "state_class" text,
  "vacator" text,
  "reason_for_change" text,
  "successor" text,
  "date_of_successor_s_formal_installation" text
);
SELECT "reason_for_change" FROM "senate" WHERE "state_class"='tennessee (2)';