## Core Concept
Cestodes, also known as tapeworms, are a class of parasitic flatworms that belong to the phylum Platyhelminthes. They are characterized by their long, flat, ribbon-like bodies and are typically found in the intestines of vertebrates. Cestodes have a complex life cycle that involves multiple hosts.

## Why the Correct Answer is Right
The correct answer, *Fasciola hepatica*, is a type of trematode, not a cestode. Trematodes, or flukes, are another class of parasitic flatworms that are distinct from cestodes. *Fasciola hepatica*, also known as the liver fluke, infects the liver of mammals, including humans, and has a different morphology and life cycle compared to cestodes.

## Why Each Wrong Option is Incorrect
* **Option A:** *Taenia saginata* (beef tapeworm) is indeed a cestode. It infects humans and cattle, causing taeniasis.
* **Option B:** *Diphyllobothrium latum* (fish tapeworm) is also a cestode, known for causing vitamin B12 deficiency in humans.
* **Option D:** *Echinococcus granulosus* (dog tapeworm) is a cestode as well, responsible for cystic echinococcosis or hydatid disease in humans.

## Clinical Pearl / High-Yield Fact
A key point to remember is that cestodes typically require an intermediate host for their larval stages, which contrasts with trematodes like *Fasciola hepatica* that often have a more direct life cycle involving mollusks as intermediate hosts. This distinction is crucial for understanding the epidemiology and control measures of these parasites.

## Correct Answer Line
**Correct Answer: C. Fasciola hepatica**