**Core Concept**
Acute hepatitis B infection is a clinical condition characterized by the sudden onset of liver inflammation due to hepatitis B virus (HBV) infection. This condition requires prompt diagnosis and treatment to prevent severe liver damage and its consequences.

**Why the Correct Answer is Right**
The correct answer is a marker that is elevated in the serum during acute HBV infection. This marker is the HBV surface antigen (HBsAg), which is a protein on the surface of the HBV particle. The presence of HBsAg in the serum indicates that the individual is infected with HBV and is in the acute phase of the disease. HBsAg is typically detected in the serum 1-4 weeks before the onset of jaundice and liver enzyme elevation, making it an important marker for early diagnosis of acute hepatitis B.

**Why Each Wrong Option is Incorrect**
* **Option A:** HBV e-antigen (HBeAg) is a marker of viral replication and is often present in patients with acute hepatitis B, but it is not as specific for acute infection as HBsAg.
* **Option B:** Anti-HBs (antibody to HBsAg) is a marker of immunity to HBV, either due to vaccination or recovery from past infection. It is not a marker of acute infection.
* **Option C:** Anti-HBc (antibody to HBcAg) is a marker of past or current HBV infection, but it does not distinguish between acute and chronic infection.

**Clinical Pearl / High-Yield Fact**
In patients with acute hepatitis B, a high level of HBV DNA in the serum is associated with a higher risk of fulminant liver failure and death. Monitoring HBV DNA levels is an important part of managing patients with acute hepatitis B.

**Correct Answer:** D.