गारो, खासी और जयंतिया पहाड़ियों की जनजातियाँ मुख्य रूप से किस प्रजातीय (Racial) समूह से संबंधित हैं?

Which one of the following pastoral nomadic tribes is historically renowned as 'hereditary horse riders' of the Central Asian steppes?

According to official census data and demographic records, which of the following Scheduled Tribes is the most populous tribe in India?