Which tapeworm is acquired through the ingestion of medium-rare steak?

The tapeworm acquired through the ingestion of medium-rare steak is Taenia saginata. This species, commonly known as the beef tapeworm, infects humans when they consume undercooked or raw beef containing the larval form of the parasite, known as cysticerci.

When the contaminated meat is ingested, the cysticerci develop into adult tapeworms within the human intestine, leading to an infection called taeniasis. This infection can result in various gastrointestinal symptoms, although many individuals may remain asymptomatic.

In contrast, the other tapeworms mentioned have different modes of transmission or hosts. Taenia pisiformis primarily infects rodents and is transmitted through undercooked or raw rabbit meat. Diphyllobothrium latum is associated with the consumption of raw or undercooked fish, not beef. Hymenolepis nana, known as the dwarf tapeworm, is primarily transmitted through the fecal-oral route rather than consumption of meat.

Therefore, the association of Taenia saginata specifically with beef consumption makes it the correct answer in this context.