CREATE TABLE table_41909 ("Week" FLOAT, "Date" TEXT, "Opponent" TEXT, "Result" TEXT, "Attendance" FLOAT)

What is Opponent, when Date is December 18, 1988?
SELECT "Opponent" FROM table_41909 WHERE "Date" = 'december 18, 1988'
SELECT "Opponent" FROM "table_41909" WHERE "Date" = 'december 18, 1988'