**Core Concept**
Hepatitis B virus (HBV) replication is a critical process that involves the production of viral particles, including DNA and proteins. This process is essential for the virus to infect new cells and spread within the body.

**Why the Correct Answer is Right**
Hepatitis B replication is indicated by the presence of HBV DNA in the blood, which is a marker of active viral replication. This can be detected using polymerase chain reaction (PCR) or other molecular techniques. Additionally, elevated levels of HBV surface antigen (HBsAg) and e-antigen (HBeAg) in the blood also indicate active replication. These markers are often used to monitor the effectiveness of antiviral therapy and to determine the risk of transmission to others.

**Why Each Wrong Option is Incorrect**
**Option A:** While this option might seem plausible, it is actually not a direct indicator of HBV replication.
**Option B:** Elevated liver enzymes, such as alanine aminotransferase (ALT), can be a sign of liver damage caused by HBV infection, but they do not directly indicate viral replication.
**Option C:** This option is actually a marker of HBV replication, as it is a protein expressed by the virus during active replication.

**Clinical Pearl / High-Yield Fact**
It's essential to note that HBV replication can be monitored using a combination of laboratory tests, including HBV DNA PCR, HBsAg, and HBeAg levels.

**Correct Answer:** C. HBsAg.