What is the average weight of the player with a height of 180 cm and plays the d position?
CREATE TABLE "list_of_united_states_national_ice_hocke" (
  "position" text,
  "jersey_number" real,
  "name_v_t_e" text,
  "height_cm" real,
  "weight_kg" real,
  "birthplace" text,
  "2008_09_team" text,
  "nhl_rights_if_any" text
);
SELECT AVG("weight_kg") FROM "list_of_united_states_national_ice_hocke" WHERE "height_cm"=180 AND "position"='d';