**Core Concept**
Substrate-level phosphorylation is a type of phosphotransfer reaction in metabolic pathways, where a high-energy phosphate group is directly transferred from a substrate to ADP or GDP, generating ATP or GTP. In glycolysis, this process occurs at two key steps, one involving phosphoglycerate kinase and the other involving pyruvate kinase.

**Why the Correct Answer is Right**
Substrate-level phosphorylation in glycolysis is primarily facilitated by the enzymes phosphoglycerate kinase (PGK) and pyruvate kinase (PK). PGK catalyzes the conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate, generating one ATP molecule per molecule of substrate. Pyruvate kinase then catalyzes the transfer of a phosphate group from phosphoenolpyruvate (PEP) to ADP, producing one ATP molecule per molecule of substrate. These reactions are crucial for the net production of ATP in glycolysis.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not specify the correct enzyme involved in substrate-level phosphorylation in glycolysis.
* **Option B:** This option is incorrect because it does not accurately describe the process of substrate-level phosphorylation in glycolysis.
* **Option D:** This option is incorrect because it is a different type of reaction that occurs in glycolysis, not a substrate-level phosphorylation reaction.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that substrate-level phosphorylation is a high-energy, ATP-producing process that occurs in glycolysis, which is essential for cellular energy production.

**Correct Answer: C. Pyruvate kinase**