**Core Concept**
The question tests the knowledge of antiviral drugs with dual activity against two major viral infections, Hepatitis B Virus (HBV) and Human Immunodeficiency Virus (HIV). This concept is crucial in the management of co-infected patients, where a single drug can target both viruses, reducing the treatment burden and improving adherence.

**Why the Correct Answer is Right**
The correct answer is a combination of Tenofovir and Emtricitabine (Truvada). Tenofovir is a nucleotide reverse transcriptase inhibitor (NtRTI) that inhibits the replication of HIV by blocking the reverse transcriptase enzyme. Emtricitabine is a nucleoside reverse transcriptase inhibitor (NRTI) that also inhibits HIV replication. Both drugs have shown efficacy in suppressing HBV replication, making Truvada a dual-active antiviral drug for co-infected patients.

**Why Each Wrong Option is Incorrect**
* **Option A:** Lamivudine is a nucleoside reverse transcriptase inhibitor (NRTI) that is effective against HIV and HBV. However, it is not a combination of two drugs with dual activity.
* **Option B:** Efavirenz is a non-nucleoside reverse transcriptase inhibitor (NNRTI) that is effective against HIV but not HBV.
* **Option D:** Raltegravir is an integrase strand transfer inhibitor (INSTI) that is effective against HIV but not HBV.

**Clinical Pearl / High-Yield Fact**
When managing co-infected patients with HBV and HIV, always consider dual-active antiviral drugs like Truvada, which can simplify treatment regimens and improve patient adherence.

**Correct Answer:** C.