**Core Concept**
Ribosomes are complex molecular machines responsible for protein synthesis in eukaryotic and prokaryotic cells. They are attached to specific cellular structures to facilitate the translation of messenger RNA (mRNA) into specific sequences of amino acids, which ultimately form proteins.

**Why the Correct Answer is Right**
In eukaryotic cells, ribosomes are primarily attached to the endoplasmic reticulum (ER), a network of membranous tubules that serves as a factory for protein synthesis and folding. This attachment is mediated by the signal recognition particle (SRP) and the SRP receptor, which ensures that newly synthesized proteins are properly targeted to the ER for processing and secretion. The ER provides a platform for ribosomes to synthesize proteins that are destined for the secretory pathway, including hormones, enzymes, and membrane proteins.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because ribosomes are not primarily attached to the mitochondria, although some ribosomes may be found in the mitochondrial matrix.
* **Option B:** This option is incorrect because ribosomes are not attached to the lysosomes, which are involved in cellular digestion and degradation of macromolecules.
* **Option C:** This option is incorrect because ribosomes are not attached to the Golgi apparatus, which is involved in protein modification, sorting, and packaging.

**Clinical Pearl / High-Yield Fact**
The ER is often referred to as the "rough endoplasmic reticulum" due to the presence of ribosomes on its surface, which gives it a characteristic rough appearance under the electron microscope. This is a key distinguishing feature of the ER from the smooth endoplasmic reticulum, which lacks ribosomes.

**Correct Answer:** C.