NIMCET 2022 — General English PYQ

The correct option is (c) is attending because the subject of the sentence is "The principal," which is singular, and the phrase "along with his assistants" is a parenthetical phrase that does not change the number of the subject. Therefore, the singular verb "is attending" should be used to agree with the singular subject. 
Explanation of Subject-Verb Agreement:
Identify the Subject: In the sentence, the main subject is "The principal".
Identify Phrases that Don't Affect the Subject: The phrase "along with his assistants" acts as additional information and does not change the fact that the principal is the singular subject.
Match the Verb to the Subject: Since the subject "The principal" is singular, the verb must also be singular.
Choose the Correct Verb Form: Out of the given options, "is attending" is the singular form of the verb that agrees with "the principal".