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Usage and Grammar
Q. Please give me your thoughts on subject/verb agreement in the following construction: “History, and the efforts of many people, [have or has] given this island a valuable gift.” Does an and phrase set off in commas change the number of the verb?
A. It doesn’t. Treat the text between commas as though it were in parentheses. But while you’re at it, notice that the construction is awkward. You aren’t sure which verb to use because neither singular nor plural sounds or looks right. That means no matter which you choose, some readers are also going to think it doesn’t sound right. It would be better to use parentheses or reword the sentence.