Final answer:
The subunit of the E. coli polymerase that confers specificity to transcription is the Sigma factor (A). The Sigma factor helps the polymerase recognize and bind to specific DNA promoter sequences, allowing the initiation of transcription from the appropriate sites.
Step-by-step explanation:
The subunit of the E. coli polymerase that confers specificity to transcription is the Sigma factor (A).
The E. coli polymerase is composed of five subunits, two of which are identical. Four of these subunits, denoted α, α, β, and β', comprise the polymerase core enzyme. Each subunit has a unique role; the two α subunits assemble the polymerase on the DNA; the β subunit binds to the ribonucleoside triphosphate that will become part of the new mRNA molecule; and the β' binds the DNA template strand.
The fifth subunit, Sigma factor (σ), is involved only in transcription initiation and confers transcriptional specificity. It helps the polymerase recognize and bind to specific DNA promoter sequences, allowing the initiation of transcription from the appropriate sites.
Therefore answer is A) Sigma factor.