Parole can be said as a temporary grant of leave to the prisoners who have committed some crime and were sentenced to imprisonment but due to their good behavior or due to genuine reasons they can be set free temporarily on certain conditions.
The federal parolees were being released in large numbers and the New York parole bureau was unable to appoint enough officers to keep track of released prisoners.
Therefore OPTION B "The Parole Bureau is unable to hire more parole officers". is correct.
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