What is the difference between a credit score and a credit rating?

a. a credit score and a credit rating are the same thing.
b. a credit score is a measure of how much debt you have, and a credit rating is a measure of your creditworthiness.
c. a credit score is a number indicating your creditworthiness, and a credit rating is a measurement of how your credit score compares to others.
d. a credit score is a measurement of your creditworthiness from one major credit bureau, and a credit rating is a measurement of your creditworthiness from all three major credit bureaus.