**Core Concept**
Zidovudine and didanosine are nucleoside reverse transcriptase inhibitors (NRTIs) used in Highly Active Antiretroviral Therapy (HAART) for the treatment of HIV infection. They work by inhibiting the replication of retroviruses through interference with the viral reverse transcription process.

**Why the Correct Answer is Right**
NRTIs, including zidovudine and didanosine, act by incorporating themselves into the viral DNA chain, leading to chain termination and thus inhibiting viral replication. This occurs because they lack a 3'-hydroxyl (-OH) group, which is necessary for the addition of another nucleotide to the growing DNA chain. As a result, the viral DNA synthesis is halted, and the virus is unable to replicate effectively.

**Why Each Wrong Option is Incorrect**
**Option A:** This option would be incorrect because zidovudine and didanosine do not act as protease inhibitors, which are a different class of antiretroviral drugs that target a different step in the viral replication cycle.

**Option B:** This option is incorrect because zidovudine and didanosine do not act as integrase inhibitors, which are another class of antiretroviral drugs that target the integration of viral DNA into the host cell genome.

**Option C:** This option is incorrect because zidovudine and didanosine do not act as entry inhibitors, which are a class of antiretroviral drugs that target the entry of the virus into the host cell.

**Clinical Pearl / High-Yield Fact**
NRTIs, including zidovudine and didanosine, can cause mitochondrial toxicity as a side effect, leading to lactic acidosis and other metabolic disturbances. This is a critical consideration in the management of patients taking these medications.

**Correct Answer: C. Inhibition of viral reverse transcription.**