What is the primary role of the sigma subunit in prokaryotic RNA polymerase?

Explanation

Option A is incorrect because Rifampicin binds to the beta subunit, not sigma. Option B is incorrect since a-amanitin inhibits eukaryotic RNA polymerase II, not the sigma subunit. Option C is correct because the sigma factor directs RNA polymerase to the specific promoter sequences for transcription initiation. Option D is incorrect because the sigma subunit is not part of the core enzyme but associates transiently.