**Core Concept**
The question is testing the understanding of alkaptonuria, a rare genetic disorder caused by the deficiency of homogentisate 1,2-dioxygenase (HGD) enzyme. This enzyme is crucial for the breakdown of tyrosine and phenylalanine, and its deficiency leads to the accumulation of homogentisic acid.

**Why the Correct Answer is Right**
In alkaptonuria, homogentisic acid accumulates and is excreted in the urine. Over time, this leads to the darkening of urine, cartilage, and other connective tissues. The accumulated homogentisic acid also undergoes oxidative polymerization, forming a pigment that deposits in various tissues, resulting in ochronosis. Ochronosis is characterized by the bluish-black pigmentation of cartilages and other connective tissues.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not relevant to the question. It might be a distractor related to another metabolic disorder.
* **Option B:** This option is incorrect because it is not directly related to the accumulation of homogentisic acid. While it might be a consequence of the disorder, it is not the primary clinical condition associated with homogentisic acid accumulation.
* **Option C:** This option is incorrect because it is a different genetic disorder altogether. While it might have some similarities with alkaptonuria, it is not caused by the accumulation of homogentisic acid.

**Clinical Pearl / High-Yield Fact**
A key clinical feature of alkaptonuria is the darkening of urine, which can be detected by the patient or healthcare provider. This is often the first sign of the disorder, prompting further investigation.

**Correct Answer: C. Alkaptonuria.**