• The phrase "an official, general forgiveness declared by the State" refers to a government's act of granting pardon to a large group of people, usually for political offences.
• The word "Amnesty" means an official pardon granted by a government to individuals or groups for past offences.
• Therefore, it is the most appropriate one-word substitution.
• Hence, Option (b) "Amnesty" is the correct answer.

Additional Information

• Option (a) Parole — Incorrect. It means the conditional release of a prisoner before the completion of their sentence.
• Option (b) Amnesty — Correct. It means an official, general pardon granted by the State.
• Option (c) Clemency — Incorrect. It means mercy or leniency shown to an individual, usually by a person in authority.
• Option (d) Remission — Incorrect. It means a reduction or cancellation of a punishment, sentence, or debt.