**Core Concept**
Cysticercosis is a parasitic infection caused by the larval stage of a tapeworm. The parasite invades the muscles, brain, and other organs of the host, leading to various clinical manifestations.

**Why the Correct Answer is Right**
The correct answer is Taenia solium, a type of tapeworm that is commonly found in pork. The larval stage of Taenia solium is known as Cysticercus cellulosae. When ingested, the eggs of Taenia solium hatch into larvae, which penetrate the intestinal wall and migrate to various parts of the body, where they form cysts. This process is facilitated by the enzyme cysticercosis antigen B (AgB), which is produced by the larvae.

**Why Each Wrong Option is Incorrect**
* **Option A:** Toxoplasma gondii is a protozoan parasite that causes toxoplasmosis, a different type of parasitic infection that is not related to cysticercosis.
* **Option B:** Echinococcus granulosus is a tapeworm that causes echinococcosis, also known as hydatid disease, which is a different type of parasitic infection.
* **Option D:** Trichinella spiralis is a type of roundworm that causes trichinosis, a different type of parasitic infection that is not related to cysticercosis.

**Clinical Pearl / High-Yield Fact**
Cysticercosis is a significant public health problem in many parts of the world, particularly in regions where pork is consumed undercooked or raw. The disease can be prevented by proper cooking of pork and adherence to good hygiene practices.

**Correct Answer: D. Trichinella spiralis is incorrect, the correct answer is Taenia solium.