**Core Concept**
The dwarf tapeworm is a type of parasitic flatworm that belongs to the genus Hymenolepis. It infects humans as an incidental host, typically through the ingestion of contaminated food or water.

**Why the Correct Answer is Right**
The correct answer refers to Hymenolepis nana, also known as the dwarf tapeworm. This parasite has a unique life cycle that involves two hosts: an intermediate host (typically insects) and a definitive host (humans). The eggs of H. nana are ingested by the intermediate host, where they develop into cysticercoids. When an infected insect is ingested by a human, the cysticercoids are released in the small intestine and develop into adult worms.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it refers to a different type of tapeworm.
**Option B:** This option is incorrect as it is not a recognized species of tapeworm.
**Option C:** This option is incorrect as it is a different type of parasitic worm.

**Clinical Pearl / High-Yield Fact**
It's essential to note that H. nana is the only tapeworm species that can complete its life cycle within a single human host, making it a significant public health concern in areas with poor sanitation and hygiene.

**Correct Answer:** D. Hymenolepis nana.