Which of the Following Statements Best Describes the Role Of \sigma

Multiple Choice

Which of the following statements best describes the role of $\sigma$ factors in bacterial gene expression?

A) " $\sigma$ factors determine which RNA polymerase is used during transcription."
B) " $\sigma$ factors mediate the excision of intronic sequences."
C) " $\sigma$ factors can be used to express certain genes necessary based on cell type."
D) " $\sigma$ factors bind to the TATA box and initiate transcription."
E) "none of the above"