Answer:
The anwer is d. contrast effects.
Step-by-step explanation:
Contrast effects are phenomena in which a person perceives a stimuls to vary in intensity or value when compared to another. For example, a very bright colour might look even brighter if placed on a dark background; or a sound may appear louder when preceded by softer sounds. In the example, the prices appear to be lower because they've been compared to higher ones.