Final answer:
In the given sentence, the correct word to fill the blank is 'retaliated'. This term signifies the staff's reaction to the boss extending their working hours.
Step-by-step explanation:
When the boss announced that everyone would have to work an hour overtime, the staff retaliated by taking a two-hour lunch. The word 'retaliated' fits into the context of the sentence and meaningfully presents a scenario where the employees responded to the boss' decision to increase their workload with an act of defiance in the form of an extended lunch break.
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