On the other hand, there is one indefinite pronoun, none, that can be either singular or plural; it often doesn't matter whether you use a singular or a plural verb — unless something else in the sentence determines its number. (Writers generally think of none as meaning not any and will choose a plural verb, as in "None of the engines are working," but when something else makes us regard none as meaning not one, we want a singular verb, as in "None of the food is fresh.")

• None of you claims responsibility for this incident?
• None of you claim responsibility for this incident?
• None of the students have done their homework. (In this last example, the word their precludes the use of the singular verb.