An association of various entities in an Entity-Relation model is known asa.Fieldb.Tuplec.Recordd.Relationship

Step 1: Break Down the Problem

The question asks to identify which term corresponds to the grouping of various entities in an Entity-Relation model.

Step 2: Relevant Concepts

In the context of an Entity-Relation (ER) model:

• Entity: Represents a real-world object or concept.
• Relationship: Represents how entities are related to one another.

Step 3: Analysis and Detail

Let's consider the definitions of the options provided:

1. Field: Represents a single piece of data, akin to a column in a database.
2. Tuple: Represents a single row in a relation, which is a set of fields.
3. Record: Often used interchangeably with tuple, representing data stored about an entity.
4. Relationship: Refers to the associations among different entities in an ER model.

Among these options, "Relationship" correctly indicates the association among various entities since it describes how multiple entities interact or relate within the model.

Step 4: Verify and Summarize

Indeed, the term that best fits the description of an association of various entities in an Entity-Relation model is "Relationship." The other terms refer to more specific components within the model rather than the associations themselves.

Final Answer

The correct answer is d. Relationship.