There’s a lot of disagreement about this one. “None” can be either singular or plural, depending on the meaning you intend and its context in the sentence. “None of the pie is left” is clearly singular. But “None of the chocolates is left” is widely accepted, as is “None of the chocolates are left.” If it’s not obvious to you which it should be, don’t worry; few of your readers will be certain either.
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