During translation initiation in prokaryotes, GTP is required for the association of the 30S-mRNA complex with formyl-met-tRNA.

**Translation Initiation in Prokaryotes:**
Translation initiation is the process by which protein synthesis begins. In prokaryotes, it involves the assembly of the ribosome on the mRNA template. The initiation complex consists of the small ribosomal subunit (30S), mRNA, and an initiator tRNA molecule loaded with the amino acid methionine (formyl-met-tRNA).

**GTP Requirement:**
GTP (guanosine triphosphate) is a nucleotide that acts as an energy source during various cellular processes. In translation initiation, GTP is required for the correct assembly of the components involved.

**Formation of the 30S-mRNA Complex:**
The first step in translation initiation is the binding of the 30S ribosomal subunit to the mRNA molecule. This interaction is facilitated by initiation factors, including IF1, IF2, and IF3. GTP is required for the association of the 30S subunit with mRNA. GTP-bound IF2 brings the formyl-met-tRNA to the ribosome, allowing it to recognize the start codon on the mRNA.

**Association of the 30S-mRNA Complex with Formyl-Met-tRNA:**
Once the 30S subunit is bound to the mRNA, GTP hydrolysis occurs, and IF2-GTP is converted to IF2-GDP. This conversion triggers the release of initiation factors from the ribosome, allowing for the binding of the formyl-met-tRNA to the start codon on the mRNA. The GTP hydrolysis is essential for the association of the 30S-mRNA complex with formyl-met-tRNA.

**Association of the 50S Subunit with the Initiation Complex:**
After the formyl-met-tRNA is positioned at the start codon, the 50S ribosomal subunit associates with the 30S-mRNA-tRNA complex, forming the functional ribosome. This association is also facilitated by GTP-dependent factors. However, GTP is not directly required for this specific step mentioned in the question.

Therefore, the correct answer is option 'C': Association of the 30S-mRNA complex with formyl-met-tRNA. GTP hydrolysis is required for the binding of the formyl-met-tRNA to the mRNA during translation initiation in prokaryotes.

The pairing of anticodon of tRNA with the mRNAs initiation codon induces binding of 50S ribosomal subunit. Thus, association of 30S mRNA with formyl-met-tRNA required GTP.

During the process of translation an initial complex is formed between mRNA. 30S ribosomal sub-unit and methionyl tRNA. This complex is formed due to the association of IF1, IF2, IF 3 initiation factors and GTP molecule.