Convert the sentence provided below from its passive voice structure to an active voice structure:
The certificates will be prepared by the office within an hour .

The correct option is: The office will prepare the certificates within an hour .

Step-by-step breakdown:

1. Identify the voice and structure of the original sentence:
The given sentence is in the passive voice: "The certificates will be prepared by the office within an hour ."
- Subject (Receiver): The certificates
- Verb Phrase: will be prepared (Simple Future Passive)
- Agent (Doer): by the office
- Time/Adverbial Phrase: within an hour .

2. Rules for converting Passive Voice to Active Voice for Simple Future Tense:
- Passive Form: Object + will + be + Past Participle (V3) + by + Subject
- Active Form: Subject + will + Base Form of Verb (V1) + Object

3. Convert to Active Voice:
- Move the agent (the office) to the subject position.
- Change the verb from "will be prepared" to the simple future active form "will prepare".
- Move the receiver (the certificates) to the object position.
- Keep the remaining temporal modifier intact (within an hour .).

Thus, the sentence in active voice becomes:
"The office will prepare the certificates within an hour ."