**Core Concept**
Nitrosoureas are a class of chemotherapeutic agents that work by alkylating DNA, causing cross-linking and subsequent DNA damage, leading to cell death. They are particularly effective against certain types of cancer, including brain tumors and lymphomas.

**Why the Correct Answer is Right**
Nitrosoureas exert their cytotoxic effects through a mechanism called alkylation, where they add an alkyl group to the DNA molecule, resulting in cross-linking and DNA damage. This process is mediated by the enzyme O6-alkylguanine-DNA alkyltransferase (AGT), which is responsible for repairing DNA damage caused by alkylating agents. However, nitrosoureas can also cause DNA damage by methylating DNA, which is facilitated by the enzyme O6-methylguanine-DNA methyltransferase (MGMT). The ability of nitrosoureas to cross the blood-brain barrier makes them effective against brain tumors.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the mechanism of action of nitrosoureas.
**Option B:** This option is incorrect because it is a different class of chemotherapeutic agents that work by inhibiting topoisomerase II, not alkylation.
**Option C:** This option is incorrect because it is a different class of chemotherapeutic agents that work by inhibiting microtubule formation, not alkylation.

**Clinical Pearl / High-Yield Fact**
Nitrosoureas are particularly effective against brain tumors due to their ability to cross the blood-brain barrier, making them a valuable treatment option for patients with glioblastoma and other brain cancers.

**Correct Answer:** C. Nitrosoureas.