In the early Middle Ages, farmers were commonly referred to as "Serfs." However, among the options you have provided, none directly refer to farmers specifically. The terms you listed (Slavs, Magyars, Muslim Arabs, Normans) refer to different ethnic groups or cultures rather than a specific occupation like farming. If the question implies another group that primarily engaged in agriculture, the closest association would be with "Slavs," as many Slavic peoples were agrarian in nature.
But please note that "Serfs" is the more accurate term for farmers in a feudal context during the Middle Ages.