Hint: It is a genus of mosquitoes, most of which are vectors of one or more major diseases of birds, humans, and other species. The diseases they carry are arbovirus infections, such as West Nile virus, Japanese encephalitis, or St. Louis encephalitis, but also filariasis and avian malaria.
In the life cycle of some parasitic nematodes, such as Wuchereria bancrofti, microfilaria is an early stage that causes a disease known as filariasis. The tissue or the vertebrate circulatory system is where adult worms live.They release microfilariae into the vertebrate host bloodstream. Microfilariae are consumed by arthropod vectors that feed on blood, most commonly by female Culex mosquitoes. The microfilariae are released into the bloodstream when a mosquito bites a healthy person,
Additional Information: Culex mosquitoes tend to have relatively blunt-shaped posterior abdomens compared to other mosquito genera and are tiny and delicate (Marshall 2006). Female mosquitoes of the subgenus Melanoconion can be classified on the basis of two unusual characteristics: 1) the thorax has a missing acrostichal setae scutum, and 2) behind the compound eyes, the head has broad, flat scales. Anopheles is a genus of mosquitoes which J. first identified and named. W. in 1818. Meigen.-Meigen. Approximately 460 species are recognised; while more than 100 are capable of transmitting human malaria, only 30-40 Plasmodium genus parasites are commonly transmitted in endemic areas , causing malaria in humans.
Hence, option A: Culex is the correct answer.
Note: The organism that causes filariasis in humans is Wuchereria bancrofti. In two hosts, the parasite terminates its life cycle. Humans act as authoritative hosts for them. The intermediate host is the Culex mosquitoes. With the aid of Culex mosquitoes, the organism transmits the disease.