Final answer:
When someone is confronted with a dangerous or frightening situation, they are most likely to start trembling due to the fight-or-flight response.
Step-by-step explanation:
In the case when someone is confronted with a dangerous or frightening situation, they are most likely to start trembling. This is because when a threat or danger is perceived, the body releases hormones that initiate the fight-or-flight response. This response prepares the body to take direct action, including trembling, in order to defend itself or run away from danger.