Final answer:
The untranslated region at the start of bacterial mRNAs is known as the 5' UTR or RNA Leader, which plays a role in RNA stability but is not translated into protein.
Step-by-step explanation:
The 5' untranslated region (5' UTR) in bacterial mRNAs is the region just upstream of the protein-coding region that is not translated into protein. This region is also referred to as the RNA Leader. The presence of RNA-binding proteins at the 5' UTR can influence the stability of the RNA molecule. Unlike a primer, which is used during DNA replication, the 5' UTR is part of the mRNA itself. It is not to be confused with codons, which are sets of three nucleotides that encode for specific amino acids during translation. Therefore, the correct answer to the student's question is c) Leader.