**Core Concept**
The Eustachian tube, or auditory tube, plays a crucial role in maintaining middle ear pressure and drainage. Its proper functioning is essential for the normal transfer of sound waves to the inner ear. Compromise of the Eustachian tube can lead to middle ear effusions and hearing difficulties.

**Why the Correct Answer is Right**
The Eustachian tube is a narrow, tortuous passage that connects the middle ear cavity to the nasopharynx. Its opening is guarded by the torus tubarius, a cartilaginous structure that can become hypertrophied in response to chronic inflammation or infection. Hypertrophy of the torus tubarius would narrow the lumen of the Eustachian tube, compromising its ability to drain the middle ear cavity and regulate pressure. This would lead to the accumulation of fluid in the middle ear, exacerbating the patient's symptoms.

**Why Each Wrong Option is Incorrect**
**Option A:** The palatine tonsil is located in the tonsillar fossa of the pharynx and is not directly related to the Eustachian tube's function or drainage.

**Option B:** The tensor veli palatini muscle is involved in the opening of the Eustachian tube, but its hypertrophy would not directly compromise the tube's drainage.

**Option C:** The cartilaginous part of the Eustachian tube is indeed critical for its function, but hypertrophy of the cartilage itself would not be the primary cause of drainage compromise.

**Clinical Pearl / High-Yield Fact**
The Eustachian tube's function can be impaired by anatomic variations, chronic inflammation, or infections. The torus tubarius is a common site for hypertrophy in response to chronic inflammation, leading to Eustachian tube dysfunction.

**Correct Answer:** C.