Consider This Problem: "Given That You Are a Bus Driver

Consider this problem: "Given that you are a bus driver, you begin the day with an empty bus. At your first stop, you let on 10 passengers. At your second stop, 4 people get off the bus, and 12 people get on. At the third stop, 8 people get off the bus, and 2 people get on. At your fourth stop, nobody gets off the bus, and 1 person gets on. How old is the bus driver?" Which of the following might prevent a person from solving this problem?

A) selective attention
B) selective encoding
C) selective comparison
D) selective combination