**Core Concept**
Zidovudine, also known as AZT, is a nucleoside reverse transcriptase inhibitor (NRTI) used in the treatment of human immunodeficiency virus (HIV) infection.

**Why the Correct Answer is Right**
Zidovudine works by inhibiting the activity of the reverse transcriptase enzyme, which is essential for the replication of retroviruses like HIV. By incorporating itself into the viral DNA, zidovudine terminates the elongation of the viral DNA chain, thereby preventing the replication of the virus. This mechanism of action makes zidovudine an effective treatment for HIV infection.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because zidovudine is not used to treat tuberculosis (TB). While TB is a significant co-infection in HIV patients, the treatment of TB involves a different class of drugs, such as isoniazid and rifampicin.
**Option B:** This option is incorrect because zidovudine is not used to treat malaria. The treatment of malaria involves antimalarial drugs like chloroquine and artemisinin, which target different pathways.
**Option C:** This option is incorrect because zidovudine is not used to treat hepatitis B. While hepatitis B and HIV can be co-infections, the treatment of hepatitis B involves nucleoside analogs like lamivudine and tenofovir, which target different pathways.

**Clinical Pearl / High-Yield Fact**
Zidovudine was the first antiretroviral medication approved for the treatment of HIV infection and has been a cornerstone of HIV treatment for over three decades.

**Correct Answer:** C. HIV infection