The best description of the initial step in the regulatory process shown below is

A) an sRNA is produced that can then be used to turn on genes.
B) an sRNA is produced that can then be used to turn off genes.
C) a sigma factor mRNA is transcribed and forms secondary structures at lower temperatures. When heated, the structures melt and the mRNA for the heat shock sigma factor, rpoH, can be translated.
D) The hairpins contain codons for a needed amino acid. When amino acid is lacking, the ribosome stalls and prevents its formation, thus allowing translation.
E) The hairpins contain codons for needed amino acids. When amino acid is present, the ribosome stalls and prevents the formation of hairpins, thus allowing translation.