In the SHELL human factors conceptual model applied in air traffic management, what does the central core 'Liveware' represent and interact with?

1. The human air traffic controller at the center, interacting with Software (procedures), Hardware (displays/consoles), Environment (workspace/climate), and Liveware (colleagues/pilots)
2. The computer central processing unit interacting solely with electrical wiring
3. The airport concrete runway interacting with heavy aircraft landing gears
4. The radar antenna array interacting with atmospheric radio wave refraction