Suppose Objects a and B Are from a User-Defined Class

Suppose objects a and b are from a user-defined class that implements the Comparable interface. What must be true about the return value of a.compareTo(b) for the compareTo method that this class implements?

A) It must return 1 if a comes before b, 0 if they are the same, and -1 if a comes after b.
B) It must return -1 if a comes before b, 0 if they are the same, and 1 if a comes after b.
C) It must return a positive value if a comes before b, 0 if they are the same, and a negative value if a comes after b.
D) It must return a negative value if a comes before b, 0 if they are the same, and a positive value if a comes after b.