CREATE TABLE "united_states_house_of_representatives_e" (
  "district" text,
  "incumbent" text,
  "party" text,
  "first_elected" real,
  "result" text,
  "candidates" text
);

Question: Who was the incumbent when ran william b. oliver (d) unopposed?
SQL: SELECT "incumbent" FROM "united_states_house_of_representatives_e" WHERE "candidates"='William B. Oliver (D) Unopposed';