Final answer:
The amygdala is the part of the brain that was involved in Trevor's fear response when he was startled by a grizzly bear in his closet. It is a key structure within the limbic system that regulates emotions like fear, and in such stressful situations, it can trigger a fight-or-flight response.
Step-by-step explanation:
When Trevor was startled to find a grizzly bear in his closet, his amygdala was involved in producing his fear response. The correct answer to the question is c. Amygdala.
The amygdala is part of the limbic system, located in the medial region of the temporal lobe. It is involved in regulating emotions, such as fear and aggression. The amygdala's role in fear response is well documented, having dense connections with sensory areas that contribute to both the emotional valuation of learning processes and memory functions. In the context of fear, it processes emotional information and, depending on the situation, can activate the sympathetic fight-or-flight response through connections with the hypothalamus and other brain systems.
Other components of the limbic system, such as the hippocampus, contribute to different aspects of memory formation but not directly to the immediate fear response that Trevor experienced.