**Core Concept**
The active site of serine proteases is a crucial region responsible for the enzymatic activity, where the substrate is cleaved through a catalytic mechanism. This region is highly specific and plays a pivotal role in the enzyme's function.

**Why the Correct Answer is Right**
The active site of serine proteases typically contains a catalytic triad consisting of a serine, a histidine, and an aspartic acid residue. This triad is essential for the hydrolysis of peptide bonds. The serine residue acts as a nucleophile, attacking the carbonyl carbon of the peptide bond, while the histidine and aspartic acid residues facilitate the protonation of the serine and the stabilization of the transition state, respectively. This unique arrangement allows serine proteases to efficiently cleave peptide bonds.

**Why Each Wrong Option is Incorrect**
* **Option A:** Incorrect because the active site of serine proteases does not contain a catalytic triad of serine, glutamic acid, and histidine.
* **Option B:** Incorrect because the active site of serine proteases does not contain a catalytic triad of asparagine, lysine, and glutamic acid.
* **Option C:** Incorrect because the active site of serine proteases does not contain a catalytic triad of cysteine, arginine, and aspartic acid.

**Clinical Pearl / High-Yield Fact**
Serine proteases play a crucial role in various physiological processes, including blood clotting, inflammation, and digestion. Understanding the structure and function of their active sites is essential for the development of therapeutic strategies to modulate their activity in different disease states.

**Correct Answer:** C. A catalytic triad of serine, histidine, and aspartic acid.