**Core Concept**
The slapped cheek sign is a clinical manifestation associated with a specific infectious disease, characterized by a distinctive erythematous rash on the cheeks, resembling the appearance of being slapped. This sign is a result of the disease's impact on the vascular endothelium and the immune response.

**Why the Correct Answer is Right**
The slapped cheek sign is a hallmark feature of Fifth Disease, also known as erythema infectiosum, caused by Parvovirus B19. The virus primarily targets erythrocyte precursors, leading to a temporary anemia and the characteristic rash. The immune response, particularly the activation of T-cells and the release of cytokines, contributes to the development of the rash. The erythematous rash appears on the cheeks due to the accumulation of immune complexes and the involvement of the vascular endothelium.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the slapped cheek sign is not commonly associated with Kawasaki disease, which presents with a different set of clinical features, including fever, lymphadenopathy, and desquamation.

**Option B:** This option is incorrect because roseola infantum, caused by human herpesvirus 6, typically presents with a high fever followed by a rash, but it does not exhibit the characteristic slapped cheek sign.

**Option C:** This option is incorrect because measles presents with a different type of rash, which is often described as maculopapular and starts on the face before spreading to other parts of the body.

**Option D:** This option is incorrect because scarlet fever, caused by group A beta-hemolytic streptococci, presents with a rash that is often described as sandpapery and starts on the trunk before spreading to other areas.

**Clinical Pearl / High-Yield Fact**
Fifth Disease can cause a temporary anemia in pregnant women, which may lead to complications in the fetus, such as hydrops fetalis. Therefore, it is essential to diagnose and manage Fifth Disease promptly in pregnant individuals.

**Correct Answer: C. Measles**