Explanation
The insect responsible for the spread of Kala-azar is Phlebotomus argentipus, also known as sand flies (Option B).
Kala-azar, also called visceral leishmaniasis, is a parasitic disease caused by the protozoan parasite Leishmania donovani. The disease is transmitted by the bite of infected sand flies of the genus Phlebotomus in the Old World and Lutzomyia in the New World.
Option A (Musca domestica) is the common housefly, which is known to spread various diseases like typhoid fever, cholera, and dysentery, but it is not responsible for the spread of Kala-azar.
Option C (Glossina palpalis) is the tsetse fly, which is responsible for transmitting African trypanosomiasis or sleeping sickness,
and Option D (Cimex lectularis) is the bed bug, which feeds on the blood of humans and animals, but it is not known to spread Kala-azar.
Therefore, the correct answer is Option B (Phlebotomus argentipus).
