Which is not a basic construct of an E-R model?a.Identifiersb.Entity typesc.Relationshipsd.Attributes

To identify which option is not a basic construct of an Entity-Relationship (E-R) model, let's analyze each of the given options:

1. Identifiers: In an E-R model, identifiers are crucial as they allow us to uniquely distinguish between different entities. They help in maintaining the integrity of the data model.

2. Entity types: These are fundamental components of an E-R model. Entity types define the various entities in the database and represent real-world objects or concepts.

3. Relationships: Relationships in an E-R model illustrate how different entities interact with one another. They are indeed a basic construct of the E-R model.

4. Attributes: Attributes provide more information about entity types. They define the properties or details of entities, making them a necessary part of the E-R model.

Conclusion:

From the analysis, all the options provided (Identifiers, Entity types, Relationships, Attributes) are indeed constructs of an E-R model. However, if any of these were to be considered "not basic," it would typically be Identifiers, because while they are important, they are not categorized as a primary construct in the same way as Entities, Relationships, and Attributes.

Final Answer:

a. Identifiers is not typically considered a basic construct of an E-R model.