To answer this question, we need to understand the relationship between the given rivers and the corresponding individuals.
The river Bhagirathi is associated with Bhagirath. Bhagirath is a king in Hindu mythology who is credited with bringing the river Ganga (which is called Bhagirathi in its initial course) from heaven to earth.
Similarly, we need to find the individual who is associated with the river Saraswati.
Option A) Kashyap - This option is correct. Kashyap is a sage in Hindu mythology who is associated with the river Saraswati.
Option B) Saraswat - This option is incorrect. While the name "Saraswat" sounds similar to "Saraswati," there is no known individual in Hindu mythology named Saraswat who is associated with the river Saraswati.
Option C) Vashishth - This option is incorrect. Vashishth is a sage in Hindu mythology, but he is not specifically associated with the river Saraswati.
Option D) Vrigu - This option is incorrect. Vrigu is a sage in Hindu mythology, but he is not specifically associated with the river Saraswati.
The correct answer is Option A) Kashyap. This option is correct because Kashyap is the sage associated with the river Saraswati.