Which one of the following sentences contains an error in its verb?

A. Not only the players but also coach Jarvis was late for practice.

B. Both Clara and Nathan is planning to attend.

C. Either footnotes or endnotes are acceptable.

D. Neither bananas nor squash was for sale

The correct answer is B. Both Clara and Nathan is planning to attend. Instead, "is" should be "are." This is because you can replace "Clara and Nathan" with "they." They are makes sense, not they is. Additionally, the word "both" signifies that the subject is plural, meaning the verb should also be plural.