Final answer:
Miss Cantrell's use of stickers as a reward for staying seated and completing worksheets represents a conditioned (secondary) reinforcer in operant conditioning terms.
Step-by-step explanation:
Miss Cantrell is using stickers to reward first-graders who exhibit the desired behavior in her classroom. In terms of operant conditioning, the stickers represent a conditioned (secondary) reinforcer. A primary reinforcer is something that has innate reinforcing qualities, such as food or water, which are not what the stickers represent. Instead, stickers have no inherent value and are only reinforcing because they are linked to a primary reinforcer, such as the pleasure the first-graders get from receiving them or what they can get in exchange for the stickers later on. Therefore, the correct answer is d. conditioned (secondary) reinforcer.