CREATE TABLE table_14939 ("Year" FLOAT, "Entrant" TEXT, "Chassis" TEXT, "Engine" TEXT, "Points" FLOAT)

What entrant had a chassis of Maserati 250f in 1954?
SELECT "Entrant" FROM table_14939 WHERE "Chassis" = 'maserati 250f' AND "Year" = '1954'
SELECT "Entrant" FROM "table_14939" WHERE "Chassis" = 'maserati 250f' AND "Year" = '1954'