Which of the Following Is an Example of Discrimination in Operant

Which of the following is an example of discrimination in operant conditioning?

A) After you have learned to operate one brand of computer, you quickly learn to operate another brand as well.
B) You have learned to buy Ida brand potato chips, which are always fresh, and to avoid Hoe brand, which are usually stale.
C) After you shifted from using one brand of computer to using another, you found that you made certain mistakes when you returned to the first brand.
D) After you ate some stale potato chips, you found that you were thirstier than usual.