The combination of nobles and knights created which group? royals peasants vassal lords

Combining nobles and knights must have created the lords. It couldn't have created the royals because knights weren't always of royal blood. It certainly couldn't have created the peasants as they already existed at a much lower status than either Knights or nobles who would not have moved down in status through combining. I don't think it is vassals because vassals were landholders who owed allegiance but again not all knights owned land so that rules them out. That leaves the group called "lords". Lords are still in existence today and people are still "nobles" and are still knighted by royalty. So that makes "Lords" the most correct answer.

Cwould be your answer