see + O + V/Ving [passive voice]

[Sitifan]

1. Someone saw John kiss Mary.
2. Someone saw Mary kissed by John.
3. John was seen to kiss Mary.
4. Mary was seen to be kissed by John.
5. Someone saw John kissing Mary.
6. Someone saw Mary being kissed by John.
7. John was seen kissing Mary.
8. Mary was seen being kissed by John.
Which of the above sentences is grammatically impossible?
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Thank you very much for your reply.

[Barb_D]

None are impossible.
#4 and #8 are the most awkward but not incorrect.