**Core Concept**
Otosclerosis is a type of bone dyscrasia affecting the middle ear, characterized by abnormal bone remodeling and deposition, leading to fixation of the stapes bone and conductive hearing loss.

**Why the Correct Answer is Right**
The tympanic membrane is usually normal in cases of otosclerosis, as the primary pathology involves the abnormal bone growth in the middle ear, specifically affecting the stapes bone and the surrounding otic capsule. The tympanic membrane is not directly involved in the disease process. However, the abnormal bone growth can cause the stapes bone to become fixed, leading to conductive hearing loss.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the tympanic membrane is not affected in otosclerosis. The primary pathology is in the middle ear bones, not the tympanic membrane.
**Option B:** This option is incorrect because the tympanic membrane is not typically perforated in otosclerosis. The disease process primarily affects the middle ear bones, not the tympanic membrane's integrity.
**Option C:** This option is incorrect because the tympanic membrane is not usually retracted in otosclerosis. The disease process primarily affects the middle ear bones, not the tympanic membrane's position or mobility.

**Clinical Pearl / High-Yield Fact**
It's essential to distinguish otosclerosis from other middle ear pathologies, such as otitis media with effusion or perforated eardrum, which may present with similar symptoms but have different underlying causes.

**Correct Answer: C. Normal**