Final answer:
The line signifies privilege and hierarchy among the animals on the farm, with the pigs establishing themselves as the ruling class.
Step-by-step explanation:
The significance of the line stating that 'all pigs, of whatever degree, were to have the privilege of wearing green ribbons on their tails on Sundays' in Animal Farm Chapter 9 is that it represents a form of privilege and hierarchy among the animals on the farm. The pigs, who have become the ruling class, are giving themselves a special privilege that sets them apart from the other animals. This privilege symbolizes their power and control over the other animals.