1. I saw a UFO in the sky yesterday.
2. I saw a UFO in the air yesterday.
3. I saw two UFOs in the sky yesterday.
4. I saw two UFOs in the air yesterday.
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Which expressions are correct?
2. I saw a UFO in the air yesterday.
3. I saw two UFOs in the sky yesterday.
4. I saw two UFOs in the air yesterday.
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Which expressions are correct?