**Core Concept**
Fungal corneal ulcers are a type of infectious keratitis caused by fungal pathogens, typically presenting with a specific set of clinical and histopathological features. The correct identification of these features is crucial for diagnosis and management.

**Why the Correct Answer is Right**
Fungal corneal ulcers typically exhibit features such as:
- A large, central, or peripheral ulcer with feathery or irregular borders
- A white or yellowish exudate with a feathery or fluffy appearance
- A significant number of fungal hyphae and spores on corneal scrapings or biopsy
- A lack of response to antibiotic therapy
- A history of trauma, contact lens use, or prior ocular surgery

**Why Each Wrong Option is Incorrect**
* **Option A:** A small, peripheral, and linear ulcer might be characteristic of a bacterial corneal ulcer. Fungal ulcers often have a more irregular and feathery appearance.
* **Option B:** A white or yellowish exudate can be seen in both fungal and bacterial ulcers, so this feature alone is not sufficient to distinguish between the two.
* **Option C:** A significant number of fungal hyphae and spores on corneal scrapings or biopsy is a key diagnostic feature of fungal corneal ulcers. This option is actually a characteristic of fungal ulcers, making it incorrect as a choice.

**Clinical Pearl / High-Yield Fact**
When diagnosing a corneal ulcer, remember the "FUNGUS" mnemonic:
- **F**ever
- **U**ltrastructural features (such as hyphae and spores)
- **N**o response to antibiotics
- **G**ranulomatous inflammation
- **U**ltrastructural examination (such as confocal microscopy)
- **S**uspicion of trauma or contact lens use

**Correct Answer: C. A significant number of fungal hyphae and spores on corneal scrapings or biopsy is a feature of fungal corneal ulcers.