## Core Concept
Protein synthesis, also known as protein biosynthesis, is the process by which cells build proteins. This process involves the transformation of a DNA sequence into a sequence of amino acids that make up a protein. The two main locations for protein synthesis in eukaryotic cells are the **rough endoplasmic reticulum (RER)**, which has ribosomes attached to it, and the **free ribosomes** found in the cytoplasm.

## Why the Correct Answer is Right
The correct answer, **C. Ribosomes**, is right because ribosomes are the cellular organelles responsible for protein synthesis. They read messenger RNA (mRNA) sequences and assemble the corresponding amino acids to form a polypeptide chain, which then folds into a protein. Ribosomes can be free-floating in the cytoplasm or attached to the endoplasmic reticulum.

## Why Each Wrong Option is Incorrect
- **Option A:** Lysosomes are membrane-bound organelles responsible for cellular digestion and recycling of macromolecules. They are not involved in protein synthesis.
- **Option B:** The Golgi apparatus is involved in protein modification, sorting, and packaging but not in the synthesis of proteins themselves.
- **Option D:** Mitochondria are known as the powerhouses of the cell and are involved in energy production. While they do have their own ribosomes for synthesizing some of their own proteins, the majority of protein synthesis in the cell occurs in ribosomes found in the cytoplasm or attached to the RER.

## Clinical Pearl / High-Yield Fact
A key point to remember is that **rough endoplasmic reticulum (RER)** is studded with ribosomes and is the site of protein synthesis for proteins that are secreted or embedded in membranes. This is a critical distinction for understanding cellular function and is often tested in exams.

## Correct Answer: C. Ribosomes