**Core Concept**
The case describes a child with a high fever, febrile seizure, and a generalized papular rash, which suggests a diagnosis related to a specific infectious or inflammatory condition.

**Why the Correct Answer is Right**
The child's symptoms are classic for **Roseola infantum**, a viral exanthem caused by human herpesvirus 6 (HHV-6) or human herpesvirus 7 (HHV-7). The high fever, which often peaks around 104°F to 105°F, is followed by a sudden drop in temperature and the appearance of a generalized papular rash. The rash typically appears after the fever has resolved and is often described as "rose-colored" or "slate-gray."

**Why Each Wrong Option is Incorrect**
**Option A:** Scarlet fever is characterized by a distinctive "strawberry tongue" and a sandpapery rash, which is not described in this case.
**Option B:** Measles typically presents with a Koplik spot on the buccal mucosa, a cough, and a distinctive rash that starts on the face and spreads to other areas of the body.
**Option C:** Fifth disease (erythema infectiosum) is caused by parvovirus B19 and is characterized by a "slapped-cheek" appearance and a lacy rash.

**Clinical Pearl / High-Yield Fact**
Roseola infantum is a common cause of febrile seizures in young children, and the rash often appears as a "post-febrile" rash, meaning it appears after the fever has resolved.

**Correct Answer:** C.