Which of the following cis-acting elements typically resides adjacent to or overlaps with many prokaryotic promoters?

Operator resides adjacent to or overlaps with many prokaryotic promoters. Operator site should be free for the movement of RNA polymerase. Operator region is unique for prokaryotic operons. Eukaryotes do not contain operator elements in the genome. Operator locus exhibit two-fold symmetry and an inveed palindrome.