In order for transcription to begin, the DNA-duplex must be "opened" to allow RNA polymerase access to single stranded template. All facilitate "opening" of DNA-duplex EXCEPT:
A) low melting temperature, Tm, in the Pribnow box. B) A:T rich DNA duplex. C) negative supercoiling. D) binding of RNA polymerase σ-subunit. E) all are true.