Final answer:
The lowest grade of nobility is the Baron. Nobility refers to a social rank that determines privileges and eligibility for official posts in the bureaucracy.
Step-by-step explanation:
The lowest grade of nobility is the Baron. In this context, the term nobility refers to a social rank that determined many aspects of one's life in terms of privileges and eligibility for official posts in the bureaucracy. The nobles were exempt from labor for the state or military service, and enjoyed certain legal advantages compared to commoners.