Concept:The phrase "not one" is singular, so the verb must be singular ("was"), not plural ("were").
Explanation:The subject is "Not one" (meaning "no single person").
"Not one" is always singular, even though it is followed by "of the hundreds of striking workers".
The verb must agree with the singular subject "one", not with the plural noun "workers".
Therefore, the correct verb is "was allowed", not "were allowed".
The error is in part (c).
The corrected sentence: "Not one of the hundreds of striking workers was allowed to go near the factory."
Answer:C