In the following question, a sentence is divided into four parts. Choose the part of the sentence which may contain a grammatical error in it. If all the parts of the sentence are grammatically correct and contextually meaningful, choose option “No error” as the answer choice.
One of the students (A)/ have failed (B)/ in the examination (C)/ this year. (D)

The correct option is B.

Step-by-step Explanation:
1. Identify the Subject: In the phrase "One of the students", the head noun of the subject is the pronoun "One", which is singular. The plural noun "students" is part of the prepositional phrase "of the students" modifying the pronoun, and does not determine the number of the verb.
2. Apply Subject-Verb Agreement: Since the subject ("One") is singular, it requires a singular verb to maintain subject-verb agreement.
3. Detect the Error: Part (B) contains the phrase "have failed". Here, "have" is a plural auxiliary verb, which incorrectly agrees with "students" instead of the singular subject "One".
4. Formulate the Correction: The plural auxiliary verb "have" must be replaced with its singular counterpart, "has". Thus, the grammatically correct sentence is: "One of the students has failed in the examination this year."