The correct answer is option 4, Sandfly. Sandflies are known to be the vector, or carrier, of Kala-azar. Kala-azar, also known as Visceral leishmaniasis, is a parasitic disease caused by the Leishmania donovani parasite. The sandfly becomes infected with the parasite when it bites an infected human or animal, and then it can transmit the parasite to another person when it bites them. Sandflies are typically active during the evening and night-time hours, and they are commonly found in tropical and subtropical regions. It is important to note that Kala-azar is not transmitted through mosquitoes like Anopheles or Culex, or the Tse-Tse fly.