The correct answer is d) translation.
Protein synthesis is a fundamental biological process through which cells generate new proteins. This occurs in two main stages: transcription and translation. During transcription, the DNA sequence of a gene is copied into messenger RNA (mRNA). This mRNA then travels from the nucleus to the cytoplasm, where translation takes place.
In translation, the mRNA serves as a template for assembling amino acids into a polypeptide chain, which then folds into a functional protein. Thus, while transcription is the first step that leads to protein synthesis, it is translation that directly involves the synthesis of proteins, making it the correct choice.