Which of the following is a helminth disease?

Where do the infective larvae of Wuchereria bancrofti mature?

Elephantiasis (filariasis) is caused by which worm?

Ascariasis is caused by an endoparasite of human $...A...$ commonly called $...B...$ Here $A$ and $B$ refer to:

Swelling of the limbs, breasts, etc., due to the blockage of lymphatic vessels is a symptom of:

Assertion $A$: Elephantiasis is a fatal disease.
Reason $R$: Filarial worms reside in the lymphatic vessels and lymph nodes.
Which option is correct for Assertion $A$ and Reason $R$?