Filaria is caused by?

Filaria (filariasis) is a parasitic disease caused by nematode worms (Wuchereria bancrofti) transmitted through the bite of infected mosquitoes, primarily Culex, Anopheles, and Aedes species. The mosquitoes inject immature worms into the bloodstream, which mature and reproduce, causing lymphatic damage and elephantiasis. Option B correctly identifies the vector, not the pathogen itself.