**Core Concept**
The **tympanogram** is a graphical representation of the movement of the eardrum and middle ear system in response to changes in air pressure, providing valuable information about middle ear function. A **C-shaped curve** or **type C tympanogram** indicates Eustachian tube dysfunction.

**Why the Correct Answer is Right**
A type C tympanogram is characterized by a peak compliance that occurs at a negative pressure, typically below -200 daPa, indicating that the middle ear system is not able to equalize pressure effectively. This is often seen in conditions where there is Eustachian tube dysfunction, such as in otitis media with effusion.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because a type A tympanogram is normal, with a single peak at or near atmospheric pressure.
**Option B:** Incorrect because a type B tympanogram is flat, indicating no movement of the eardrum and middle ear system, often seen in otitis media with effusion but not specifically with Eustachian tube dysfunction as indicated by a C-shaped curve.

**Clinical Pearl / High-Yield Fact**
It's crucial to remember that tympanometry is a valuable diagnostic tool for assessing middle ear function and that different tympanogram types correspond to specific middle ear conditions, aiding in the diagnosis and management of hearing and ear-related disorders.

**Correct Answer:** D. Eustachian tube dysfunction