Which one of the following causes kala-azar?

The correct option is C Leishmania
Kala-azar, also known as visceral leishmaniasis is a condition of chronic, systemic disease, transmitted by the sandfly vector. It is caused by protozoan parasites of the genus Leishmania. Main symptoms of kala-azar comprise of high fever, extensive weight loss, swelling of the spleen and liver, anemia, bleeding, wasting, weakness, darkening of skin and swollen glands.