Can we use past participls after before?
He finished his work before his boss arrived.
Or
He finished his work before his boss arrives.
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Sign up to join this communityCan we use past participls after before?
He finished his work before his boss arrived.
Or
He finished his work before his boss arrives.
No, you can't use a past participle there.
Before is followed by either a noun phrase (eg "before lunch"; "before his arrival") or a finite clause (a clause with a finite verb - eg "before I arrive"; "before they eat").
The clause following before in both your examples is fine: "before his boss arrives" (so-called "present tense") and "before his boss arrived" (past tense - not past participle).
However, the second sentence doesn't make sense, because "he finished" is past, and "before his boss arrives" is future.* The first sentence is fine, and almost certainly what you wanted to say.
*You may be surprised that I say this is future. I guess most people will say it is present, because it contains the so-called present tense. I say that it is either timeless-habitual ("Every day he finishes his work before his boss arrives") or future ( "He'll finish his work before his boss arrives"). It's hard to come up with a context in which it can have present meaning.
The first sentence
He finished his work before his boss arrived.
is good. The second sentence would be better as
He finishes his work before his boss arrives.
being a present tense narrative.
Both sentences now use the same tense in each part.