**Core Concept**
Zidovudine is a nucleoside reverse transcriptase inhibitor (NRTI) used in the treatment of HIV infection. Resistance to zidovudine occurs due to mutations in the HIV reverse transcriptase gene that alter the enzyme's ability to bind to the drug.

**Why the Correct Answer is Right**
The most common mutation associated with zidovudine resistance is the M41L mutation in the HIV-1 reverse transcriptase gene. This mutation leads to a change in the enzyme's conformation, making it less susceptible to inhibition by zidovudine. As a result, the virus is able to replicate more efficiently, leading to treatment failure. The M41L mutation is typically seen in combination with other mutations, such as D67N, K70R, and T215F/Y, which further contribute to zidovudine resistance.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because while mutations in the HIV reverse transcriptase gene can lead to resistance to other NRTIs, such as lamivudine or abacavir, they are not the primary cause of zidovudine resistance.
**Option B:** This option is incorrect because the M184V mutation is associated with resistance to lamivudine, not zidovudine.
**Option C:** This option is incorrect because the K65R mutation is associated with resistance to tenofovir, a nucleotide reverse transcriptase inhibitor, not zidovudine.

**Clinical Pearl / High-Yield Fact**
The development of zidovudine resistance is often accompanied by cross-resistance to other NRTIs, highlighting the importance of using combination antiretroviral therapy and monitoring for resistance mutations.

**Correct Answer:** M41L