**Core Concept**
The patient's symptoms, particularly the musty odor and black headed filamentous growth resembling wet blotting paper, suggest a fungal infection of the external auditory canal. This condition is characterized by an overgrowth of fungi, leading to inflammation and discharge.

**Why the Correct Answer is Right**
The presence of a musty odor and black headed filamentous growth is classic for otomycosis, a fungal infection of the external auditory canal. The growth of fungi, such as Aspergillus or Candida, can cause itching, earache, and discharge. The black headed filamentous growth resembles wet blotting paper due to the presence of fungal hyphae. Otomycosis can be caused by exposure to water, humidity, or trauma to the ear canal.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it refers to a bacterial infection of the external auditory canal, which typically presents with a foul odor and a thick, yellow or greenish discharge.

**Option B:** This option is incorrect as it refers to a viral infection of the external auditory canal, which typically presents with a sudden onset of ear pain and hearing loss.

**Option C:** This option is incorrect as it refers to a foreign body in the external auditory canal, which typically presents with a sudden onset of ear pain and hearing loss.

**Clinical Pearl / High-Yield Fact**
Otomycosis can be diagnosed based on clinical presentation and confirmed by fungal culture. Treatment typically involves topical antifungal agents and removal of the fungal growth.

**Correct Answer:** C. Otomycosis.