Question

name the main rivers of the central highlands that join the ganga and the yamuna

Answer 1

The ganga is joined by many tributaries from the himalayas . a few of them being a major rivers such as the Yamuna . the ghaghara the gandak and the kosi the river Yamuna rises from yamunotri glacier in the himalayas it flows parallel of the ganga and as a right bank tributary meets the ganga at allahabad
so your answer is allahabad