If Class Dog Has a Subclass Retriever, Which of the Following

Multiple Choice

If class Dog has a subclass Retriever, which of the following is true?

A) Because of single inheritance, Dog can have no other subclasses.
B) Because of single inheritance, Retriever can extend no other class except Dog.
C) The relationship between these classes implies that Dog "is-a" Retriever.
D) The relationship between these classes implies that Retriever "has-a" Dog.