Option B, 'We had interviewed 20 people by the time we began the new project,' is the correct way to rewrite the sentence in active voice, as it makes 'we' the doer of the action 'had interviewed.'
The best way to rewrite the given sentence in active voice is: We had interviewed 20 people by the time we began the new project. This sentence makes the subject ('we') the doer of the action ('had interviewed'), which is the essential characteristic of an active voice construction. Here's why the other options don't work: Option A changes the meaning of the sentence; Option C uses passive voice ('were interviewed'); Option D retains the passive voice used in the original sentence ('had been interviewed').
When determining if a sentence is in passive voice, you should check if:
- The subject is being acted upon rather than doing the action.
- There is a form of the verb 'be' (am, is, are, was, were) used with the past participle (-ed or -en) of the verb.
- The preposition 'by [noun phrase]' either appears in the sentence or can be logically added.
In rewritings where the active voice is used effectively, sentences are typically stronger, clearer, and more concise. Moreover, they make the subject perform the action.