Given a class whose instances, when found in a collection of objects, are sorted by using the compareTo（　）method, which two statements are true?（）

A. The class implements java.lang.Comparable.

B. The class implements java.util.Comparator.

C. The interface used to implement sorting allows this class to define only one sort sequence.

D. The interface used to implement sorting allows this class to define many different sort sequences.