The sentence which uses the passive voice form is option A. A path of destruction was left by the twister. A passive voice construction has no direct object which directly receives the action of the verb. In this kind of sentence, the object becomes the subject instead.
Your answer would be A. I was just doing this. So if you read up to the comma it is a complete sentence by itself.
Answer:
When will the result be announced?
Explanation: Hope it helps
