Note that 'money a worker is compelled ..." can modify the adjective phrase: 'a deferred payment of salary', thus you can't eliminate any of the answers on plural/singular grounds.
In that case, it should be "worker". But it could also modify the whole previous clause, and "Pensions" is plural, so it should be "workers"
The sky is the limit
800 is the limit
GMAT Club Premium Membership - big benefits and savings