The correct answer is: A. Yamuna
Adi Badri is a Hindu pilgrimage site in the Garhwal Himalayas in Uttarakhand, India. It is located on the banks of the Yamuna River, about 200 kilometers (120 mi) from Haridwar. The place is associated with the Hindu god Vishnu, and is believed to be the spot where he first descended to Earth.
The Yamuna River is one of the most sacred rivers in Hinduism. It is believed to be the daughter of the sun god Surya, and is often associated with the goddess Lakshmi. The river is said to have healing powers, and is a popular spot for bathing and pilgrimage.
The other options are incorrect because they are not associated with Adi Badri. The Saraswati River is a sacred river in Hinduism, but it is not located near Adi Badri. The Markanda River is a tributary of the Yamuna River, and it is not as sacred as the Yamuna River. The Ganga River is the most sacred river in Hinduism, but it is located in a different part of India.