**Core Concept**
Hydatid disease, caused by the parasitic tapeworm Echinococcus granulosus, involves a complex life cycle with intermediate hosts. The intermediate host plays a crucial role in the development of the parasite, allowing it to mature and produce infectious cysts.

**Why the Correct Answer is Right**
The correct answer is the definitive host's feces-contaminated intermediate host, which ingests the parasite's eggs. The eggs hatch in the intermediate host's digestive tract, releasing oncospheres that penetrate the intestinal wall and enter the bloodstream. The oncospheres then lodge in the liver, lungs, or other organs, where they form cysts that grow and mature. The intermediate host's immune system does not typically eliminate the parasite, allowing it to continue its life cycle.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because the definitive host, typically a carnivore such as a dog or wolf, is not an intermediate host.
**Option B:** Incorrect because the intermediate host is not the definitive host's feces itself, but rather an organism that ingests the parasite's eggs.
**Option C:** Incorrect because the correct answer is not a specific type of intermediate host, but rather the general category of organisms that serve as intermediate hosts for the parasite.

**Clinical Pearl / High-Yield Fact**
It's essential to note that humans can act as accidental intermediate hosts, ingesting the parasite's eggs through contaminated food or water. This can lead to the formation of hydatid cysts in humans, which can cause a range of symptoms depending on the location and size of the cyst.

**Correct Answer: D. Humans (accidental intermediate hosts) or other herbivores and omnivores.**