seen/having been seen. . .

the whole place was cleaned until there was not a speck of dust . . . anywhere. see 2.seen 3.having been seen 4. to be seen
Please help me with this test!
Thanks a lot!

What do you think?
Which options can you discount?
Which ones are you confused about?
The more you do yourself, the more independent a learner you will become.

Thank you very much for your advice
I think ‘seen’ is correct

That is the second best answer.
‘To be seen’ is the standard idiomatic phrase and therefore the best answer.