Final answer:
During a small arms encounter, an officer would have the most ballistic protection behind the engine block of a vehicle because it is the densest part and can absorb or deflect bullets more effectively than other parts of a vehicle.
Step-by-step explanation:
The location that will give an officer the most ballistic protection during a small arms encounter is d. Behind the engine block. The engine block is the densest part of a vehicle and provides the most material to absorb or deflect bullets. Locations like the front seat, rear seat, or trunk offer significantly less protection compared to the metal and density of an engine block. In police and tactical training, taking cover behind the engine block is often taught as a best practice in situations involving gunfire.