**Core Concept**
Nonoxynol-9 is a type of spermicidal agent used in contraceptives to kill sperm by disrupting the cell membrane, thereby preventing fertilization. It works by causing a rapid increase in permeability of the sperm cell membrane, leading to cell lysis.

**Why the Correct Answer is Right**
Nonoxynol-9 is a detergent-like compound that disrupts the sperm cell membrane by altering the lipid bilayer structure, ultimately causing cell death. This is achieved through the interaction of nonoxynol-9 with the cholesterol molecules in the sperm cell membrane. The sperm cell membrane is rich in cholesterol, which is crucial for maintaining its integrity. When nonoxynol-9 binds to the cholesterol molecules, it creates pores in the membrane, allowing ions and water to enter the cell, leading to cell lysis.

**Why Each Wrong Option is Incorrect**
* **Option A:** This is incorrect because the specific name of the spermicidal agent is not provided. While nonoxynol-9 is a well-known spermicidal agent, other agents like octoxynol-9 or benzalkonium chloride may be used in different products.
* **Option B:** This is incorrect because there is no widely recognized spermicidal agent by this name. Nonoxynol-9 is a specific compound that has been widely used in spermicidal products.
* **Option C:** This is incorrect because the name of the spermicidal agent is not provided. While some products may contain a combination of spermicidal agents, nonoxynol-9 is a specific compound that has been widely used in spermicidal products.

**Clinical Pearl / High-Yield Fact**
Nonoxynol-9 can cause vaginal irritation and allergic reactions in some individuals, which may lead to increased risk of HIV transmission if used with latex condoms. It is essential to use spermicidal products with caution and follow the manufacturer's instructions.

**Correct Answer:** C. Nonoxynol-9