user: Question: What is the dance that has Priscilla Presley is the worst dancer(s), and the worst score of 21?
Columns: ['Dance', 'Best dancer(s)', 'Best score', 'Worst dancer(s)', 'Worst score']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['Cha-cha-cha Face-off', 'Kristi Yamaguchi Kristi Yamaguchi', '28 30', 'Penn Jillette Jason Taylor', '16 24']
SQL:

assistant: SELECT "Dance" FROM "Table" WHERE "Worst dancer(s)" = 'Priscilla Presley' AND "Worst score" = '21';