**Core Concept**
Tobacco chewing is a significant risk factor for oral squamous cell carcinoma (OSCC), a type of cancer that arises from the squamous cells lining the mucous membranes of the oral cavity. Cisplatin is a chemotherapeutic agent used in the treatment of various cancers, including OSCC.

**Why the Correct Answer is Right**
Cisplatin exerts its antitumor effects by inducing DNA cross-links, thereby inhibiting DNA replication and transcription. This is achieved through the formation of platinum-DNA adducts, which interfere with the normal functioning of DNA repair mechanisms. The resulting DNA damage triggers apoptosis in cancer cells. Specifically, cisplatin causes:
* **Interstrand cross-links**: Cisplatin forms covalent bonds between adjacent purine bases on opposite strands of DNA, preventing the strands from separating during replication.
* **Intrastrand cross-links**: Cisplatin forms covalent bonds between adjacent purine bases on the same strand of DNA, distorting the DNA double helix and interfering with transcription.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because cisplatin is known to cause interstrand cross-links, which is a correct mechanism of action.
**Option B:** This option is incorrect because cisplatin does not directly cause mutations in DNA repair genes; instead, it induces DNA damage that triggers apoptosis.
**Option C:** This option is incorrect because cisplatin is not known to cause epigenetic modifications, such as DNA methylation or histone modification.

**Clinical Pearl / High-Yield Fact**
Cisplatin is a potent chemotherapeutic agent, but it can cause severe side effects, including nephrotoxicity, ototoxicity, and neurotoxicity. To minimize these risks, patients receiving cisplatin should be closely monitored for signs of toxicity.

**Correct Answer: D.**