The iron-response element (IRE) is a(n) :

The iron-response element (IRE) is a(n)
 
  A) insulator element that binds IRE-binding protein in the absence of iron.
  B) transcriptional promoter that directly binds iron to prevent transcription of nearby genes.
  C) long noncoding RNA that binds iron and regulates transcription of multiple genes.
  D) sequence in the 5 untranslated region of mRNA that forms a hairpin loop, preventing translation of the mRNA by binding to IRE-binding protein in the absence of iron.
  E) example of a prokaryotic riboswitch that causes early termination of transcription in the presence of iron.