"Is / was / has been / had been used" in a statement

I’m confused whether I should use are or were or have been or had been in the following statement when describing the use of language in a passage

In paragraph 6, detailed adjectives ____ used to describe the scenery of the campus.

The thing is, those adjectives on the passage are/were used to describe the campus when the writer wrote them down in the past, so are they still in effect when I’m writing this sentence?

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To my knowledge, (sorry, correct me if I am wrong)

1. is used means it is currently used at present
2. was used means it was once used but no longer in effect
3. has been used means the action use started in the past and it’s still used or not used now
4. had been used means the action used started and ended the past (not used now)

At the same time, I’ve been told to use past tense when the date or time is specified and present perfect when the the time is unclear or not important Does passive voice break these rules?

I’m not quite sure in this case describing a world’s usage in a passage is a present or completed action. I’ve fit each option into the blank and I’ve had an conclusion that have been used seems fluid to me, I’m not sure and if so why others are incorrect?

Sorry asking so many questions at a time, any answer will be appreciated, thanks a lot.