Individuals with blood type ab have which blood antibody(ies)?

Which describes a promoter? a.the first part of an operon that regulates where, when, and to what level a gene is expressed b.the part of an operon that, if attached by a repressor protein, suppresses the expression of a gene c.a cluster of genes that are expressed or repressed as a group d.an enzyme that dna unzip prior to transcription