was interested in trying to get his students to spend more time studying the Malott text, so he decided to first reinforce the students when he saw them carrying their Malott book. When he passed one of the students in the hall who was carrying the Malott book, he said something like "I am glad to see you are carrying your Malott book around." The students looked puzzled, but Professor Murphy noted an increase in Malott-book-carrying behavior. Apparently, the professor believes that carrying the book around is a(n) ________________________ to the ultimate behavior of studying more.

1) approximation

2) step

3) resemblacne

4) estimation