**Core Concept**
Introns are non-coding regions of a eukaryotic gene that are removed by RNA splicing during the processing of pre-mRNA into mature mRNA. This process is crucial for generating the diverse range of proteins from a single gene through alternative splicing.

**Why the Correct Answer is Right**
The correct process of intron removal involves a complex interplay of RNA molecules and enzymes, specifically the spliceosomes. The spliceosomes recognize specific sequences within the introns, known as splice sites, and cleave the pre-mRNA at these sites. The resulting lariat structure is then removed, and the exons are joined together through a process called ligation. This process is mediated by a group of enzymes called spliceosomal RNAs (snRNAs) and the associated proteins.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify the correct enzyme or process responsible for intron removal. While ribonucleases do play a role in RNA degradation, they are not directly involved in the splicing process.
**Option B:** This option is incorrect because it is not a recognized enzyme or process involved in intron removal. The correct process involves the spliceosomes, which are distinct from the endoplasmic reticulum (ER).
**Option C:** This option is incorrect because it is a type of RNA involved in protein synthesis, not intron removal. Transfer RNA (tRNA) plays a crucial role in translating the genetic code into a specific amino acid sequence.

**Clinical Pearl / High-Yield Fact**
The process of RNA splicing is essential for generating the diverse range of proteins from a single gene. Defects in this process can lead to a range of diseases, including muscular dystrophy and certain types of cancer.

**Correct Answer: C. Spliceosomes. Spliceosomes are responsible for removing introns from pre-mRNA during the processing of genes into mature mRNA.**