What passive construction relates to the man's assistance to the police?

The correct answer effectively demonstrates a passive construction by starting with "was reported," indicating an action performed by an unspecified source regarding the man's assistance to the police. This structure emphasizes the subject's involvement -- in this case, the man -- while the focus is on the report of his actions rather than on who is reporting it.

In passive constructions, the doer of the action is often omitted or less important than the action itself, which aligns with the context that the man's assistance is being discussed in a passive voice. Therefore, using "was reported to have been helping" suggests that there is an acknowledgment of his actions without attributing the action directly to him in the sentence's structure. The use of "helping" also directly correlates with the notion of assistance.

Other options do contain elements of passive voice, but they differ in word choice and context, making them less suitable for clearly reflecting the original idea of the man's assistance.