**Core Concept**
Sofosbuvir is a direct-acting antiviral (DAA) medication used in the treatment of hepatitis C virus (HCV) infection. It belongs to the class of HCV NS5B RNA-dependent RNA polymerase inhibitors, which are essential for viral replication.

**Why the Correct Answer is Right**
Sofosbuvir works by selectively inhibiting the NS5B RNA-dependent RNA polymerase enzyme of HCV, thereby preventing the viral RNA from being replicated. This enzyme is crucial for the transcription of the viral genome into a complementary RNA strand, which is then used as a template for the production of new viral RNA molecules. By inhibiting this enzyme, sofosbuvir effectively blocks the viral replication cycle. The correct target of sofosbuvir is the HCV NS5B RNA-dependent RNA polymerase, not the HBV polymerase.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it incorrectly states that sofosbuvir inhibits RNA-dependent RNA polymerase of HBV, which is not its mechanism of action.
**Option B:** This option is incorrect because sofosbuvir is a specific inhibitor of RNA-dependent RNA polymerase, not DNA-dependent RNA polymerase, and its target is HCV, not HBV.
**Option C:** This option is incorrect because it suggests that sofosbuvir targets HBV, which is not the case.
**Option D:** This option is incorrect because it incorrectly states that sofosbuvir inhibits DNA-dependent RNA polymerase, which is not its mechanism of action.

**Clinical Pearl / High-Yield Fact**
Sofosbuvir is often used in combination with other DAAs, such as ledipasvir or daclatasvir, to achieve high cure rates in patients with HCV genotype 1 infection. The combination of sofosbuvir and ledipasvir has been shown to have a high efficacy rate, with cure rates exceeding 90% in clinical trials.

✓ Correct Answer: A. Inhibits RNA dependent RNA polymerase of HCV