What is the benefit of using @VisibleForTesting annotation?
a. to denote that a class, methods, or field has its visibility relaxed to make code testable
b. to denote that a class, method, or field is visible only in the test code
c. to denote that a class, method, or field has its visibility increased to make code less testable
d. to throw a run-time error if a class, methods, or field with this annotation is accessed improperly
