**Core Concept**
Self-splicing introns are a type of ribozyme that can catalyze their own removal from pre-mRNA molecules. This process is an essential step in the maturation of mRNA, allowing for the precise excision of introns and the joining of exons to form the final mRNA transcript.

**Why the Correct Answer is Right**
Self-splicing introns, also known as group II introns, are a class of ribozymes that can catalyze their own excision from pre-mRNA. This process involves the formation of a lariat intermediate, where the 5' end of the intron is covalently attached to the 2' hydroxyl group of an adenosine residue at the branch point. As the intron is removed, a new 5' phosphate group is formed, allowing the exons to be joined together. The removal of introns is a crucial step in the maturation of mRNA, ensuring that the final transcript is free of non-coding regions.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the term "intron that forms a ribozyme" is a bit misleading. While it is true that introns can form ribozymes, this option does not accurately describe the self-splicing activity of introns.

**Option B:** This option is incorrect because it is incomplete. While self-splicing introns are indeed ribozymes, the process of self-splicing also involves the formation of lariat intermediates.

**Option C:** This option is incorrect because it is also incomplete. While the formation of lariat intermediates is an essential step in the self-splicing process, it is not the only aspect of self-splicing introns.

**Clinical Pearl / High-Yield Fact**
The self-splicing activity of introns is an important example of the catalytic capabilities of RNA molecules, which can be harnessed for various biotechnological applications. Understanding the mechanisms of self-splicing introns can also provide insights into the evolution of RNA molecules and their role in the origin of life.

**✓ Correct Answer: D. All of these. All of the processes mentioned (self-splicing introns, formation of ribozymes, and lariat intermediates) are involved in the removal of introns from pre-mRNA molecules.**