Which of the following diseases is transmitted by mosquitoes?

Filariasis is caused by the infection of:

Which is the correct option for the vector, the infective stage of the pathogen entering the human body, and the location of the pathogen in the vector for elephantiasis?

In how many days does the filarial larva develop into an infective larva within the intermediate host (in $days$)?

Assertion $A$: In elephantiasis, body parts like legs, arms, and genital organs swell significantly.
Reason $R$: In chronic cases, filarial worms block the lymphatic vessels.
Which option is correct for Assertion $A$ and Reason $R$?

To prevent filariasis (elephantiasis), we should.........