Which of the following sentences contains a grammatical error?

The sentence "Everyone needs to bring their own lunch" is often cited as containing a grammatical error based on traditional rules of pronoun agreement. Traditionally, "everyone" is viewed as a singular pronoun, which would call for a singular pronoun referring back to it. Therefore, many believe that it should be "his or her" instead of "their." However, the use of "they" or "their" as a singular, gender-neutral pronoun has become widely accepted in modern English, as it addresses inclusivity and avoids gender specification.

In contrast, the other sentences adhere to standard grammatical rules. "Each student has his or her own locker" properly uses the singular pronoun to match "each," while "Neither of the answers is correct" correctly employs singular agreement with "neither." Finally, "All of the students have finished their exams" maintains proper plural agreement. Consequently, while "Everyone needs to bring their own lunch" might seem incorrect under traditional grammar rules, it reflects contemporary usage trends.