Protozoa may cause which of the following diseases?

Protozoa are single-celled organisms that can cause a variety of diseases in humans. Amoeba dysentery, also known as amoebic dysentery or Entamoeba histolytica infection, is caused by a protozoan and leads to severe intestinal issues, including diarrhea and abdominal pain. Giardiasis, caused by the protozoan Giardia lamblia, results in symptoms such as diarrhea, gas, and cramps, impacting the gastrointestinal tract.

The other options include diseases caused by different pathogens. Tuberculosis and pneumonia are primarily caused by bacterial infections, not protozoan infections. Malaria, while caused by a protozoan (specifically the Plasmodium species), is paired with yellow fever, which is a viral infection, making that option partially correct, but not exclusively about protozoa. Cholera and typhoid are both caused by bacteria, namely Vibrio cholerae and Salmonella typhi, respectively. Thus, the diseases listed in the correct choice are specifically linked to protozoan infections.