**Core Concept**
Dimorphic fungi are a group of fungi that can exist in two distinct forms: a yeast form and a filamentous (mold) form. This dimorphism is often temperature-dependent, with the yeast form typically found at body temperature and the mold form found at lower temperatures.

**Why the Correct Answer is Right**
The correct answer is likely to be a fungus that does not exhibit dimorphism. Dimorphic fungi include species such as *Histoplasma capsulatum*, *Blastomyces dermatitidis*, and *Coccidioides immitis*. These fungi can convert from a mold form to a yeast form at body temperature, which is a key characteristic of dimorphic fungi.

**Why Each Wrong Option is Incorrect**
**Option A:** *Histoplasma capsulatum* is a dimorphic fungus that converts from a mold form to a yeast form at body temperature, making it a characteristic example of a dimorphic fungus.
**Option B:** *Blastomyces dermatitidis* is another dimorphic fungus that exhibits temperature-dependent dimorphism, with a mold form at lower temperatures and a yeast form at body temperature.
**Option C:** *Coccidioides immitis* is a dimorphic fungus that also exhibits temperature-dependent dimorphism, with a mold form at lower temperatures and a yeast form at body temperature.
**Option D:** *Aspergillus fumigatus* is a mold that does not exhibit dimorphism and remains in a filamentous form at all temperatures. It is a correct example of a non-dimorphic fungus.

**Clinical Pearl / High-Yield Fact**
Dimorphic fungi are often found in soil and can cause opportunistic infections in humans, particularly in immunocompromised individuals. The temperature-dependent dimorphism of these fungi is a key characteristic that distinguishes them from other types of fungi.

**Correct Answer: D. Aspergillus fumigatus**