The New England Journal of Medicine (NEJM) is a weekly general medical journal that publishes new medical research and review articles, and editorial opinion on a wide variety of topics of ...
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Why is a just a rather odd wh -word. Its distribution is very limited -- it can only have the word reason as its antecedent, and since it's never the subject it's always deletable. Consequently it behaves strangely, as you and others point out.