Final answer:
Tricyclic antidepressants can impair body temperature regulation, increasing the risk of environmental hypothermia due to sedation and decreased shivering.
Step-by-step explanation:
The drug that would most likely predispose an individual to the effects of environmental hypothermia is D. Tricyclic antidepressants. These medications can impair the body's ability to regulate temperature, which can be particularly dangerous in cold environments.
Usage of tricyclic antidepressants may lead to sedation and a decrease in shivering - the body's natural response to generate heat in cold conditions. As a result, individuals taking tricyclic antidepressants may be at a higher risk for hypothermia when exposed to cold temperatures.