Name the number of episods for segment c being s oyster
CREATE TABLE "season_18_2011_2012" (
  "series_ep" text,
  "episode" real,
  "segment_a" text,
  "segment_b" text,
  "segment_c" text,
  "segment_d" text
);
SELECT COUNT("episode") FROM "season_18_2011_2012" WHERE "segment_c"='s Oyster';