During loading and unloading operations of flammable liquid road tankers under JT/T 617.6 and GB 18564.1, which safety sequence must be strictly executed BEFORE connecting loading hoses?

1. Turn off the vehicle engine, engage the parking brake, place wheel chocks (防溜车垫木), connect the static grounding clamp and verify grounding continuity, and verify the presence of fire extinguishers
2. Keep the vehicle engine running at high RPM to speed up the unloading pump
3. Light a cigarette to check the ambient wind direction
4. Disconnect the vehicle battery cables with a steel wrench to create test sparks