The correct answer is option 2: Sandfly. The sandfly is the vector for kala-azar disease, also known as visceral leishmaniasis. A vector is an organism that transfers a disease from one host to another. In the case of kala-azar, the sandfly acts as a carrier of the parasite called Leishmania donovani.

Option 1: Housefly is not the vector for kala-azar. Houseflies are known for transmitting other diseases like diarrhea and typhoid fever, but they do not play a role in spreading kala-azar.

Option 3: Aedes mosquito is not the vector for kala-azar. Aedes mosquitoes are known for transmitting diseases such as dengue fever and Zika virus, but they are not involved in the transmission of kala-azar.

Option 4: Anopheles mosquito is also not the vector for kala-azar. Anopheles mosquitoes are widely known for transmitting malaria, but they do not play a role in spreading kala-azar.

Therefore, the correct vector for kala-azar disease is the sandfly, which is responsible for transmitting the parasite to humans through its bite.