Is the following grammatically correct?

He has a bomb which no one knows how powerful it is.

I think the "it" should be removed to make it grammatically blunder-free.

  • 3
    I'm not sure why it has been migrated, but John Lawler gives the definitive answer (addressing a Ross Constraint violation) here. Islands are ELL material now? Jul 23, 2019 at 14:35
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    See this answer to a related question (not sure if it's a duplicate). Short answer - strictly speaking your example isn't syntactically valid. Something like He has a bomb the power of which / whose power no one knows would be okay. Jul 23, 2019 at 14:37
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    I've heard people painting themselves into a corner after say "He has a book on shed-building that" ['he doesn't know where he got it from'] and it's easily done. You're expecting an easy conclusion to the sentence ("[He has a book on shed-building that] he got from Blackwell's / from the market // the other day ... ") and then find there isn't one. "... from he knows not where" is fairytale, and "from an unknown source" journalese or legalese. Essentially, if you don't want a pause (stop yourself before "that", and add "– [and] he doesn't know where he got it from"), you have to start afresh. Jul 23, 2019 at 14:53

1 Answer 1


It would make sense to substitute "which" for "and".

'He has a bomb, and no one knows how powerful it is.'

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