CREATE TABLE table_31704 ("Res." TEXT, "Record" TEXT, "Opponent" TEXT, "Method" TEXT, "Event" TEXT, "Round" FLOAT, "Location" TEXT)

Which opponent has a record of 3-0?
SELECT "Opponent" FROM table_31704 WHERE "Record" = '3-0'
SELECT "Opponent" FROM "table_31704" WHERE "Record" = '3-0'