Question 16 :
An entity class is a collection of entities and is described by the structure of the entities in that class.
Question 17 :
Relationship classes are associations between entity classes.
Question 18 :
An identifier typically uses more than one attribute.
Question 19 :
An identifier determines the type of relationship that an entity has.
Question 20 :
A recursive relationship is a relationship between an archetype and an instance of that archetype.