Final answer:
Without his daily Grande Dark Roast, Raiyan's heart rate at the LiBrary spot is most likely to remain unchanged as the stimulatory effects of caffeine are absent. Option 1 is correct; there would be no change in his heart rate from caffeine simulation.
Step-by-step explanation:
If Raiyan goes to the LiBrary spot to study but Starbucks runs out of coffee, his physiological response will differ from his usual routine. Since caffeine is a psychoactive drug that has a stimulatory effect on the cardiac centers, causing an increase in heart rate (HR), the absence of caffeine means option 1 is the most likely: without coffee, his heart rate will not change due to caffeine stimulation. However, it is possible that the routine of going to the LiBrary and preparing to study could cause some anticipatory physiological responses, possibly a slight increase in HR due to the anticipation of studying, but this would not be due to the effects of caffeine. The concept of systematic desensitization (option 3) is unrelated to the scenario as it involves a therapeutic technique to reduce phobic responses, and option 4, which suggests that the stimulus of the LiBrary spot will make his heart beat decrease, does not align with the usual effects of anticipation and preparation for a focused activity such as studying.