The correct option is A The final game has been won by them.
‘The final game has been won by them.’ is the correct answer. In the passive voice, the receiver of the action, ‘The final game’ appears first in the sentence and as the receiver is singular, the singular form of the helping verb, ‘has’ is used. It is followed by the ‘be’ verb form ‘been’, the past participle of the main verb, ‘won’, the preposition ‘by’ and the doer of the action ‘they’ which changes to object pronoun ‘them’.