As Diagrammed Below, Some Amino Acid Biosynthetic Operons Have Stem

As diagrammed below, some amino acid biosynthetic operons have stem loop structures in the mRNA. These structures play a role in the regulation of the operon by which of the following mechanisms?

A) The leader sequence shown contains codons for the amino acid. When these are low, the ribosome stalls, allowing a hairpin between the two middle regions to form so that the rest of the message can be translated.
B) A repressor protein made of that amino acid will bind to the region and prevent translation when large amounts of the amino acid are present.
C) In the presence of large amounts of the amino acid, the hairpin will wind around the amino acid and prevent further translation.
D) The uridine-rich region has codons for that amino acid; when present, this region will be a terminator region. The hairpins allow for an RNA to bind that then allows translation to occur.
E) Catabolite repressor protein can bind and prevent the hairpins from forming, thus allowing translation to occur.