Final answer:
Bob and Fred reacted to the screeching of tires because it triggered a conditioned response, an automatic reaction to an auditory cue that is associated with danger in driving scenarios.
Step-by-step explanation:
The conditioned response is the reason Bob and Fred reacted to the screeching of tires at the red light, despite having clean driving records. The screeching of tires likely acted as an auditory cue that triggered a conditioned response based on their previous experiences or knowledge of driving scenarios. Although they did not have direct involvement in accidents, the sound is commonly associated with the potential for danger on the road, prompting an instinctual reaction to the possibility of an imminent threat.