The pair (baby lion cubs) was / were born in July.

Should the verb be singular or plural in this sentence?
Use the singular for "pair."

The pair was born in July.

The cubs were born in July.
American is strictly "pair is/was"
I cannot speak for BrE, but that is untrue. I am liable to use either number.
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There is a difference in American and British usage. American is strictly "pair is/was", British English will often have "pair are/were". The same goes for words like team and couple.
 Mister Micawber's reply was promoted to an answer.
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