A person who wants to buy a compact disc (CD) has just enough money to buy one and chooses CD A instead of CD B. What is CD B?

CD B is the compact disc that the person did not choose to buy, despite having the option. It represents an alternative selection that the individual considered but ultimately passed over in favor of CD A. The choice signifies a preference or evaluation of the two CDs, leading to the decision to spend their limited funds on CD A.