which pollutant has the least amount of petroleum coke fired ?
CREATE TABLE table_204_909 (
    id number,
    "pollutant" text,
    "units" text,
    "emission standard" number,
    "coal-fired" text,
    "petroleum coke-fired" text
)
SELECT "pollutant" FROM table_204_909 ORDER BY "petroleum coke-fired" LIMIT 1
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: which pollutant has the least amount of petroleum coke fired ? ### Input: CREATE TABLE table_204_909 (
    id number,
    "pollutant" text,
    "units" text,
    "emission standard" number,
    "coal-fired" text,
    "petroleum coke-fired" text
) ### Response: SELECT "pollutant" FROM table_204_909 ORDER BY "petroleum coke-fired" LIMIT 1