**Core Concept**
The question tests the ability to identify the species of Shigella that do not ferment **mannitol**, a key characteristic used in the identification and classification of Shigella species. Shigella species are gram-negative, non-motile bacteria that cause **shigellosis**, a form of dysentery.

**Why the Correct Answer is Right**
Shigella species can be differentiated based on their ability to ferment various sugars, including **mannitol**. Most Shigella species, such as **Shigella flexneri** and **Shigella boydii**, ferment mannitol, while **Shigella dysenteriae** does not. This difference is crucial for laboratory identification.

**Why Each Wrong Option is Incorrect**
**Option A:** Shigella flexneri ferments mannitol, making it an incorrect choice.
**Option B:** Shigella boydii also ferments mannitol.
**Option C:** This option is not provided, but typically, other Shigella species like **Shigella sonnei** ferment mannitol as well.

**Clinical Pearl / High-Yield Fact**
Remembering that **Shigella dysenteriae** is the species that does not ferment mannitol is key, as this species is also known for producing the **Shiga toxin**, which causes severe dysentery.

**Correct Answer:** D. Shigella dysenteriae