In the given sentences, the passive voice is characterized by the fact that the subject of the sentence is being acted upon rather than performing the action. Let's analyze the two sentences provided:
1. "Gabriel must have been exhausted by that long flight to Australia."
- In this sentence, the subject "Gabriel" is being exhausted by the long flight. The focus is on what is happening to Gabriel (being exhausted), not on who or what is performing the action. Therefore, this sentence is in the passive voice.
2. "The twenty-two-hour flight to Australia must have utterly exhausted Gabriel."
- In this sentence, the subject is the "twenty-two-hour flight," which is the one performing the action of exhausting Gabriel. Gabriel is the recipient of the action (being exhausted). This sentence is in the active voice because the subject (the flight) is doing the action.
Therefore, the sentence in passive voice is:
- "Gabriel must have been exhausted by that long flight to Australia."
