Which of the following is an example of proactive interference?

a. You can’t recall your locker combination from sixth grade because your current locker combination interferes.

b. You can’t recall your new cell phone number because your old number interferes.

c. You can’t recall what you studied in first period because what you studied in fourth period interferes.

d. You can’t recall what you studied on Monday because what you studied on Tuesday interferes.

e. You can’t recall who won the state swim meet last year because the winner of this year’s meet interferes.