Famous palaeontologist / paleobotanist of India was
Birbal Sahni FRS (14 November 1891 – 10 April 1949) was an Indian paleobotanist who considered the fossils of the Indian subcontinent. He likewise appreciated topography and prehistoric studies. He established what is presently the Birbal Sahni Institute of Palaeobotany at Lucknow in 1946.
So, the correct option is 'B. Sahni'.