Which four are true？（）
A. Has-a relationships should never be encapsulated.
B. Has-a relationships should be implemented using inheritance.
C. Has-a relationships can be implemented using instance variables.
D. Is-a relationships can be implemented using the extends keyword.
E. Is-a relationships can be implemented using the implements keyword.
F. An array or a collection can be used to implement a one-to-many has-a relationship.
G. The relationship between Movie and Actress is an example of an is-a relationship.
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