In your opinion, should cellur signal disruptors be allowed in places where phone calls are perceived as annoying?

Which of these sentences has an error in subject-verb agreement? a. official procedures calls for students who are tardy three times to serve detention. b. as a result of her efforts, a team of volunteers signs up every month to clean the city's parks. c. the committee of parents protested loudly at the school board meeting. d. each of the neighbors brings a dish to share at the pot-luck gathering.

Could someone me with this question?

According to the study what did john steinbeck do to prepare for his book the grapes of wrath