After a police car with flashing lights and blaring siren passes Tom and pulls over another driver for speeding, Tom's heartbeat soon slows down, his blood pressure decreases, and he stops sweating. These calming physical reactions are MOST directly regulated by his nervous system.

Parasympathetic

Explanation:

The parasympathetic nervous system predominates in quiet “rest and digest” conditions while the sympathetic nervous system drives the “fight or flight” response in stressful situations. The main purpose of the PNS is to conserve energy to be used later and to regulate bodily functions like digestion and urination. That is why the Parasympathetic Nervous System is being used in this scenario. Hope this helped :)