How should severe, pulsating bright-red external hemorrhage from an open limb laceration be controlled immediately at a motorcycle crash scene?

1. Pour boiling water over the open wound to cauterize the blood vessels
2. Pack dirt and dry soil into the wound to encourage blood clotting
3. Leave the wound open to air and wait for emergency vehicles to arrive
4. Apply firm direct manual pressure over the wound using a sterile dressing or clean cloth, and secure with a snug pressure bandage (加压包扎止血法)