CREATE TABLE table_25446 ("Outcome" CLOB, "Year" FLOAT, "Championship" CLOB, "Surface" CLOB, "Partner" CLOB, "Opponents" CLOB, "Score" CLOB)

What is the surface when the us open is the championship in the year 1979?
SELECT "Surface" FROM table_25446 WHERE "Championship" = 'US Open' AND "Year" = '1979'
SELECT "Surface" FROM "table_25446" WHERE "Championship" = 'US Open' AND "Year" = '1979'