CREATE TABLE table_55718 ("Match" FLOAT, "Date" TEXT, "Competition or tour" TEXT, "Ground" TEXT, "Opponent" TEXT, "Score1" TEXT)

Which opponent has a date 21 jul 2007?
SELECT "Opponent" FROM table_55718 WHERE "Date" = '21 jul 2007'
SELECT "Opponent" FROM "table_55718" WHERE "Date" = '21 jul 2007'