The causal organism of Kala-azar is
Leishmania donovani
The correct option is C.
Explanation for the correct option:
Explanation for the incorrect options:
Option A:
Plasmodium vivax is the second most common cause of malaria worldwide.
Option C:
Trypanosoma levisi is a trypanosomas of the sub-genus Herpetosoma, a parasite of rats transmitted by fleas.
Option D:
Wuchereria bancrofti is a filarial worm found in human lymph nodes that causes lymphatic filariasis .
Final answer: The causal organism of Kala-azar is Leishmania Donovani.