Choice "B" is correct. All of the statements are correct. Program modification controls are controls over the modification of programs being used in production applications. Program modification controls include both controls that attempt to prevent changes by unauthorized personnel and also that track program changes so that there is an exact record of what versions of what programs were running in production at any specific point in time. Program change control software normally includes a software change management tool and a change request tracking tool. Program change control often involves changing what are effectively the same programs in two different ways simultaneously. Normally, an environment has both production programs and programs that are being tested. Sometimes, production programs require changes (production fixes) at the same time the test versions of the same programs are being worked on. This process must be controlled so that one set of changes does not incorrectly overlay the other.Choices "c", "d", and "a" are incorrect, per the above explanation.