Identify the segment of the sentence which contains a grammatical error.
Not a single boy in the unruly class raised their hands before answering the question.

Correct option is D

Option (d) contains an error.
Explanation:
The phrase "Not a single boy" is singular in meaning, so any pronoun referring back to it must also be singular.
However, "their hands" is a plural pronoun and doesn’t agree with the singular subject.
Correct sentence:
Not a single boy in the unruly class raised his hand before answering the question.
Grammatical rule used:
Singular indefinite expressions like "no one, not a single, each, every" must be followed by singular pronouns.
Example:
· Incorrect: Not a single girl brought their umbrella.
· Correct: Not a single girl brought her umbrella.