Which of the following diseases is caused by a helminth?

Taeniasis is an infection caused by tapeworms, which are a type of helminth. Helminths are large, multicellular organisms that can be parasitic, living in a host organism and deriving nutrients at the host's expense. In the case of Taeniasis, the infection occurs when humans ingest undercooked or contaminated meat containing the larval forms of the tapeworm, leading to gastrointestinal issues and other health complications.

In contrast, malaria is caused by a protozoan parasite known as Plasmodium, while AIDS is caused by the human immunodeficiency virus (HIV), a retrovirus. Tuberculosis is caused by the bacterium Mycobacterium tuberculosis. Thus, while the other diseases are caused by microorganisms from different groups—protozoa, viruses, and bacteria—Taeniasis distinctly stems from a helminth, making it the correct answer.