After Hiking to a Remote Area and Setting Up Camp

Multiple Choice

After hiking to a remote area and setting up camp, Brendan and Beth, who are regular coffee drinkers, discovered that they had not packed any coffee. Over the next few days, both Beth and Brendan had constant low-intensity headaches and felt groggy, sleepy, and listless. Beth and Brendan were experiencing:

A) caffeine psychosis.
B) drug relapse.
C) tolerance.
D) withdrawal symptoms.