What is the surface when the us open is the championship in the year 1979?
CREATE TABLE table_25446 (
    "Outcome" text,
    "Year" real,
    "Championship" text,
    "Surface" text,
    "Partner" text,
    "Opponents" text,
    "Score" text
)
SELECT "Surface" FROM table_25446 WHERE "Championship" = 'US Open' AND "Year" = '1979'
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: What is the surface when the us open is the championship in the year 1979? ### Input: CREATE TABLE table_25446 (
    "Outcome" text,
    "Year" real,
    "Championship" text,
    "Surface" text,
    "Partner" text,
    "Opponents" text,
    "Score" text
) ### Response: SELECT "Surface" FROM table_25446 WHERE "Championship" = 'US Open' AND "Year" = '1979'