The correct option is A will be purified
<!--td {border: 1px solid #cccccc;}br {mso-data-placement:same-cell;}-->
The correct answer is ‘will be purified’. In passive voice, the receiver of the action ‘The water’ appears first in the sentence. It is followed by ‘will be’, the past participle of the verb ‘purify’, ‘purified’, the preposition ‘by’ and the doer of the action ‘Aquabot’.