Consider the following assertion :
In the Pleistocene period either the Yamuna once flowed into the Indus, or the Sutlej flowed into the Yamuna and one major tributary of either had shifted from the Ganga to the Indus or vice versa.
Which of the following is/are the basis of the above assertion ?
1. The Nadi-Sukta of the Rigveda
2. The explorations of the Sutlej and the Yamuna by Robert Bruce Foote
3. The presence of the same species of dolphins in both the Indus and the Ganga river systems
Select the answer using the code given below :

What does an empty seat represent in early Buddhist iconography ?