Read the excerpt from The Communist Manifesto. Let the ruling classes tremble at a Communistic revolution. The proletarians [workers] have nothing to lose but their chains. They have a world to win. Working men of all countries, unite!

What is the best meaning of “The proletarians have nothing to lose but their chains”?

Workers should take care not to lose their personal property.
Workers are so oppressed that they should revolt.
A failed revolt will land the revolutionaries in prison, in chains.
It is unjust to hold communist revolutionaries in chains.