In the provided sentence, we need to identify which part contains an error. Let's break it down:
One of the student forgot: This phrase is incorrect because "student" is singular, but "one of the" suggests that we are talking about a group of students. The correct phrase should be "One of the students forgot," where "students" is the plural form, indicating that the subject is part of a larger group.
to submit one of the assignments: This part of the sentence is correctly structured. It clearly states the action that was not completed.
causing concern among the faculty members: This phrase is also correctly formed. It effectively conveys the result of the previous action.
In summary, while most parts of the sentence are correct, one specific area fails to maintain subject-verb agreement, which is crucial for grammatical accuracy.