TRUE : FALSE :: BUSY :

1. idle
2. metropolis
3. alive
4. vacation

True and “false” are logical opposites. “Busy” and “idle” describe activity levels. “Metropolis” is a city type, unrelated. “Alive” contrasts with “dead,” not “busy.” “Idle” perfectly opposes “busy” in denoting inactivity. So, TRUE : FALSE :: BUSY : IDLE.