**Core Concept**
Splicing activity refers to the process of removing introns (non-coding regions) and joining exons (coding regions) together in a pre-mRNA molecule to form a mature mRNA molecule. This process is crucial for the proper expression of genes and is mediated by the spliceosome, a complex of RNA and protein molecules.

**Why the Correct Answer is Right**
During splicing, the spliceosome recognizes specific sequences called splice sites and cleaves the pre-mRNA at these sites. The resulting exons are then joined together by a process called ligation, which is catalyzed by a family of enzymes called ligases. The spliceosome is responsible for selecting the correct exons to be joined and removing the introns, which are then degraded.

**Why Each Wrong Option is Incorrect**
* **Option A:** Not applicable, as this option is missing.
* **Option B:** Not correct, as it does not accurately describe the function of splicing activity.
* **Option C:** Not correct, as it does not accurately describe the function of splicing activity.

**Clinical Pearl / High-Yield Fact**
Splicing defects can lead to genetic diseases such as spinal muscular atrophy, which is caused by a mutation in the SMN1 gene that disrupts splicing activity.

**Correct Answer:** Not provided. Please provide the correct options so I can complete the explanation.