Dаn is very excited аbоut аn upcоming rоck concert he and a couple of friends are going to attend. The concert is about 30 miles away, and they are going to go in one of his friend’s small 2-door sports car. On the evening of the concert, Dan is riding in the back seat of the small car–it is a little cramped in the back, but he is excited to get to the concert. On the way to the concert, the driver loses control, and there is a serious accident. Dan is the most injured with severe head injury and a broken back. Following a year of recovery, Dan is walking one day in his small town when a small car pulls up and offers him a ride. Dan sees the small car and is filled with anxiety as he realizes he has a strong small car phobia. He refuses the ride in the small car and as the car drives away, he notices that his anxiety starts to go away. Read and answer the following classical conditioning questions to help explain his anxiety and small car phobia. In the above story, what is the unconditioned stimulus (US)?