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The noun pair can be followed by a singular or plural verb. The singular is always used when pair refers to a set considered as a single entity: This pair of shoes is on sale.
A plural verb is used when the members are considered as individuals: The pair are working more harmoniously now.
After a number other than one, pair itself can be either singular or plural, but the plural is now more common: She bought six pairs (or pair) of stockings.
