Final answer:
In the context of entity-relationship diagrams, Unary, Binary, and Ternary are valid degrees of relationships, while 'N-ary' is not a specific degree but rather a term for any relationships with more than two entities. Therefore, N-ary is not a valid degree of relationship in this context.
Step-by-step explanation:
The student has asked a question regarding the validity of certain degrees of relationships in the context of data modeling, specifically related to entity-relationship diagrams or databases. Unary, binary, and ternary are all valid degrees of relationships that can exist between entities in a database. A unary relationship involves one entity type, a binary relationship involves two entity types, and a ternary relationship involves three entity types. However, 'N-ary' as a specific term is not typically used to represent a degree of relationship; rather it represents a concept or a general term for any degree of relationship greater than binary (including ternary and beyond). Therefore, in the context provided, assuming that we mean a specific degree, 'N-ary' would not be a valid answer and the correct response is C) N-ary.