Who were the expert horse riders that came to India from the north

Explanation:

Three mounted Comanche warriors, 1892. The horse was a key element in Comanche culture, who are thought to have been the first of the Plains Indians to have horses.

The Aryans were the expert horse riders that came to India from the north

a historian researching the immigration policies of the early 1900s would expect a source written today,rather than in 1910 to :

( a ) be more interested in objective data and statistics.