What equipment is primarily used during an ASM smog check inspection?

The correct choice indicates that the equipment primarily used during an ASM (Acceleration Simulation Mode) smog check inspection is a combination of an Emission Inspection System (EIS) machine and a dynamometer.

During an ASM inspection, vehicles are subjected to a test that simulates real-world driving conditions to measure emissions more accurately. The dynamometer allows the vehicle to be driven in a controlled environment while the EIS machine captures the emissions data produced during the test. This setup is critical because the dynamometer simulates acceleration, allowing inspectors to evaluate how emissions change under various load conditions, which is essential for understanding a vehicle's environmental impact.

While other equipment, such as visual inspection tools and handheld diagnostic tools, plays a role in vehicle evaluations, they do not provide the specific testing and simulation capabilities that the EIS and dynamometer do. This makes the combination of an EIS machine with a dynamometer the primary tools used during an ASM smog check inspection because they are designed specifically for detailed emissions analysis under simulated operational conditions.