Which of the following cell organelles play the most significant role in protein synthesis ?

Option 2 is correct. Ribosomes are the molecular machines that translate mRNA into polypeptide chains and are the primary sites of protein synthesis in the cell [2]. Many ribosomes attach to the rough endoplasmic reticulum (RER); the RER provides a membrane surface and translocation machinery for cotranslational insertion and processing of proteins destined for membranes or secretion, so the RER and its bound ribosomes work together in synthesis of these proteins [1]. The Golgi apparatus acts mainly in post‑synthetic modification, sorting, and shipping of proteins rather than their primary synthesis [3]. Thus, endoplasmic reticulum (RER) plus ribosomes are the organelles most significant for protein synthesis.

Sources

1. [2] https://med.libretexts.org/Courses/Skyline_College/Human_Physiology_for_Allied_Health_Professionals/03%3A_The_Cellular_Level_of_Organization/3.03%3A_The_Cytoplasm_and_Cellular_Organelles
2. [1] https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/rough-endoplasmic-reticulum
3. [3] https://opentext.csu.edu.au/secretlivesofcells/chapter/the-endomembrane-system/