Regression testing refers to

a) re-testing a program after fixing a problem to ensure that the fix worked and that it did not introduce another problem.
b) executing the statements in the program in reverse order.
c) executing the program on many different types of computers and comparing the results.
d) running a program with many different sets of inputs.
e) None of these describes regression testing

a) re-testing a program after fixing a problem to ensure that the fix worked and that it did not introduce another problem.