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 Rigveda2.The explorations of the Sutlej and the Yamuna by Robert Bruce Foote3.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:

1. A

   1 only

   This option claims that only statement 1 forms the basis of the assertion. The Nadi-Sukta hymn of the Rigveda lists rivers from east to west (including Ganga, Yamuna, Sutlej, Indus), but it is a sacred geographical hymn and does not constitute scientific or geological evidence of Pleistocene river captures. Therefore, statement 1 is incorrect as a geological basis.

2. B

   2 only

   This option claims that only statement 2 forms the basis of the assertion. Robert Bruce Foote was a pioneering British geologist and archaeologist known for discovering the first Paleolithic stone tool in India at Pallavaram and working with the Geological Survey of India, but he did not establish the Pleistocene river capture hypothesis based on river explorations. Therefore, statement 2 is incorrect.

3. C

   1 and 2

   This option claims that both statements 1 and 2 form the basis of the assertion. Since neither the Nadi-Sukta hymn nor the geological explorations of Robert Bruce Foote serve as the empirical basis for this specific Pleistocene river capture hypothesis, this combination is incorrect.

4. D

   3

   The presence of the same species of freshwater dolphins (Platanista gangetica) in both the Indus and the Ganga-Brahmaputra river systems provides crucial biological and zoogeographical evidence supporting the historical shifting and interconnection of these river basins during the Pleistocene period. Therefore, statement 3 alone forms the basis of the assertion.

Summary. Official key is (d). The evolutionary and distributional evidence of freshwater dolphins across major northern river systems serves as a primary biological indicator of ancient river captures, while Rigvedic hymns and early archaeological surveys do not provide the geological basis for this phenomenon.