Before entering the Northern Plains of Uttar Pradesh, the River Sarda is known as Kali. It is important to note that the River Saraswati is a separate river and not the same as the River Sarda. The River Saraswati is believed to be an ancient river that has dried up and is considered sacred in Hindu mythology. Bhagirathi, on the other hand, is a river in Uttarakhand and is one of the main tributaries of the River Ganga. Pindar is also a river in Uttarakhand, but it is not associated with the River Sarda.

Therefore, the correct answer is option 3 - Kali.