Topic: Subject Verb Agreement,

Best Answer Explained in Below-:

The correct answer to the question is A) "problems is," but this answer contains an error in its structure and may not seem grammatically correct at first glance. Let's clarify why the correct answer should reflect a correct subject-verb agreement.

In standard English grammar, "problems" is a plural noun and should be paired with a plural verb. Therefore, the correct structure would actually be to use "are." However, if we assume the intention behind "problems is" was to singularize it as "problem," which is common when singularizing a statement for emphasis, the correct answer would likely be D) "problem is."

The phrase "One of the crucial problems" implies that while there are multiple problems, we are discussing one specific problem that is significant or critical. In that case, we would use "is" to align the singular subject "one" with the verb.

Hence, the accurate completion of the phrase would read: "One of the crucial problems is traffic jam." Here, "problems" being plural refers to the broader category of issues related to traffic, while "is" correctly connects to the singular subject "one." This emphasizes the specific issue of traffic jam as a significant concern.

It’s important to always ensure that subjects and verbs agree in number for grammatical accuracy, especially in sentences that involve phrases like "one of the."