user: Question: What team was the opponent for the game played on December 19, 1999?
Columns: ['Week', 'Date', 'Opponent', 'Result', 'Attendance']
Types: ['real', 'text', 'text', 'text', 'text']
Sample row: [1.0, 'September 12, 1999', 'Arizona Cardinals', 'L 25–24', '64,113']
SQL:

assistant: SELECT "Opponent" FROM "Table" WHERE "Date" = 'December 19, 1999';