These questions always bug me when they ask about a perfectly normal, acceptable English usage.
It just seems like someone whose English isn't that good decided to question the correctness of the writing of someone else who ex hypothesi has a better grasp of English, and then decided to waste our time with it. There also seem to be a lot of them, asking about perfectly acceptable English, which doesn't do anyone but the questioner any good, and they could probably just have used google or a reference work to find the answer to their question, without cluttering up the site.
Can we introduce a policy requiring that these questions specify why there is some doubt as to the acceptability of the construct in question? That would at least allow the answers to be more useful by explaining the questioner is under a misapprehension as to the rules applicable.
Examples:
Is it correct to say "one out of *a* possible four"?
https://english.stackexchange.com/questions/23768/is-please-ensure-parity-amongst-all-correct/23781
Is the phrase "man is mortal" grammatically correct?
Some examples where the poster has put at least a minimal explanation for their doubt: