Termination of Transcription in E $\sigma$ ) Factor to the End of the MRNA

Termination of transcription in E. coli is signaled by

A) formation of a stem-loop structure in the RNA.
B) binding of Rho protein to the end of the mRNA.
C) binding of a sigma ( $\sigma$ ) factor to the end of the mRNA.
D) an inverted GC-rich sequence followed by seven A residues.