Anticodons are complementary to proline mRNA codons, written 3' to 5'.

Steps:

• Recall proline mRNA codons: CCU, CCC, CCA, CCG.
• For codon CCA, find direct complements: C pairs G, C pairs G, A pairs U.
• Form anticodon 3'-GGU-5', denoted as GGU in this notation.
• Select matching choice D.

Why D is correct:

• GGU is the 3'–5' sequence directly complementary to proline codon CCA via Watson-Crick base pairing (G-C, G-C, U-A).

Why the others are wrong:

• A. CCA: mRNA codon for proline, not anticodon.
• B. CCU: mRNA codon for proline, not anticodon.
• C. GGT: Uses DNA base T instead of RNA base U.

Final answer: D