Explanation/Reference:
A: JPA 2.0 defines an ElementCollection mapping. It is meant to handle several non-standard relationship mappings. An ElementCollection can be used to define a one-to-many relationship to an Embeddable object, or a Basic value (such as a collection of Strings). An ElementCollection can also be used in combination with a Map to define relationships where the key can be any type of object, and the value is an Embeddable object or a Basic value.
D:
Example of an ElementCollection relationship database:

Example of an ElementCollection relationship annotations
@ Entity
public class Employee {
@Id
@Column(name="EMP_ID")
private long id;
...
@ElementCollection
@CollectionTable(
name="PHONE",
joinColumns=@JoinColumn(name="OWNER_ID")
)
private List<Phone> phones;
...
}
@Embeddable
public class Phone {
private String type;
private String areaCode;
@ Column(name="P_NUMBER")
private String number;
...
}
Reference: Java Persistence/ElementCollection