Mrs. Dean's algebra students typically have a difficult time with word problems, often getting lost in the process. She wants to keep them from giving up, so when they first start doing them, she gives a point on the problem if they just manage to get the problem started. Later, she requires that they get the problem "set up" correctly in order to get any points, and finally they must solve the problem to earn points. Mrs. Dean's procedure is most precisely described as:

a. increasing a behavior through classical conditioning. 

b. increasing a behavior through negative reinforcement. 

c. increasing a behavior through extinction 

d. increasing a behavior through shaping