**Core Concept**
Chronic hepatitis B requires antiviral therapy to suppress viral replication and prevent liver damage. Elevated serum AST levels indicate liver inflammation, necessitating treatment that targets the underlying viral infection.

**Why the Correct Answer is Right**
The correct answer is **Entecavir**. Entecavir is a potent nucleoside analog that inhibits the hepatitis B virus (HBV) DNA polymerase, thereby reducing viral replication. Its high potency and low resistance rate make it an ideal choice for patients with chronic hepatitis B, including those with elevated AST levels. Entecavir is particularly effective in suppressing HBV DNA levels and slowing disease progression.

**Why Each Wrong Option is Incorrect**
**Option A:** **Lamivudine** is an older antiviral agent that was widely used for HBV treatment. However, its resistance rate is higher compared to Entecavir, making it a less optimal choice for patients with chronic hepatitis B.

**Option B:** **Interferon-alpha** is an immunomodulatory therapy that can stimulate the host immune response against HBV. However, its efficacy is lower compared to antiviral agents like Entecavir, and it may not be suitable for patients with elevated AST levels.

**Option C:** **Ribavirin** is an antiviral agent used primarily for treating hepatitis C virus (HCV) infection. It is not indicated for the treatment of chronic hepatitis B.

**Clinical Pearl / High-Yield Fact**
In patients with chronic hepatitis B, it is essential to monitor liver function tests (LFTs) regularly, as elevated AST levels can indicate disease progression. Antiviral therapy with agents like Entecavir can help suppress HBV replication and prevent further liver damage.

**Correct Answer:** C. Entecavir