Which statements best describe the Gang of Four design patterns called Memento and Observer?
Memento captures and restores an object's internal state. Observer notifies multiple classes of changes.
Memento alters an object's behavior when its state changes. Observer encapsulates an algorithm inside a class.
Memento defers the exact steps of an algorithm to a subclass. Observer defines a new operation to a class without change.
Memento notifies multiple classes of changes. Observer captures and restores an object's internal state.