**Core Concept**
The clinical presentation suggests a diagnosis of **Primary Herpetic Gingivostomatitis**, a common viral infection in children characterized by oral ulcers, fever, and crusting of the lips. This condition is caused by the **Herpes Simplex Virus (HSV)**.

**Why the Correct Answer is Right**
The treatment plan for Primary Herpetic Gingivostomatitis typically involves symptomatic relief, as the infection is self-limiting. This may include antipyretics for fever, topical anesthetics for pain relief, and antiviral medications such as **acyclovir** to reduce the severity and duration of symptoms.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because the treatment does not typically involve antibiotics, as this is a viral infection.
**Option B:** Incorrect as corticosteroids are not the first line of treatment for this condition.
**Option D:** Incorrect because, although antivirals may be considered, the question lacks a specific antiviral option, making it an incomplete choice.

**Clinical Pearl / High-Yield Fact**
It's crucial to differentiate Primary Herpetic Gingivostomatitis from other causes of oral ulcers, such as **Aphthous Ulcers** or **Hand, Foot, and Mouth Disease**, to provide appropriate treatment and reassure the patient and their family about the self-limiting nature of the condition.

**Correct Answer:** D. Acyclovir.