**Core Concept**
The question is testing the knowledge of antimetabolite antineoplastic agents used in the treatment of mesothelioma, a type of cancer that affects the lining of the lungs or abdomen. Antimetabolites are a class of chemotherapeutic agents that inhibit DNA synthesis by interfering with the production of nucleotides.

**Why the Correct Answer is Right**
Pemetrexed is a folate analog antimetabolite that is used in the treatment of malignant pleural mesothelioma. It works by inhibiting the enzyme thymidylate synthase, which is necessary for DNA synthesis. By blocking this enzyme, pemetrexed prevents the production of thymidine, a nucleotide required for DNA replication. As a result, cancer cells are unable to divide and grow, leading to tumor shrinkage and improved survival.

**Why Each Wrong Option is Incorrect**
* **Option A:** Cisplatin is a platinum-based chemotherapeutic agent that is used to treat various types of cancers, including ovarian, lung, and testicular cancer. However, it is not typically used in the treatment of mesothelioma.
* **Option B:** Gemcitabine is a nucleoside analog antimetabolite that is used to treat pancreatic and breast cancers, but not mesothelioma.
* **Option D:** Vinorelbine is a vinca alkaloid that is used to treat breast and lung cancers, but not mesothelioma.

**Clinical Pearl / High-Yield Fact**
Pemetrexed is often used in combination with cisplatin for the treatment of malignant pleural mesothelioma, and the combination has shown improved survival rates compared to pemetrexed alone.

**Correct Answer:** C. Pemetrexed