Which sentence illustrates the subjunctive mood?

The sentence that illustrates the subjunctive mood is the one that expresses a hypothetical situation or something contrary to fact. In the selected sentence, "If he were here, he would help us," the use of "were" indicates a condition that is not true at the present moment; it imagines a scenario where he is not actually present but considers what would happen if he were.

The subjunctive mood is often used in conditional statements like this one to convey wishes, demands, or hypothetical situations, which sets it apart from other moods that describe real or likely situations. The construction of this sentence highlights an unreal or indefinite state, which is a hallmark of the subjunctive mood.

Other sentences in the options state facts or predictions without expressing a condition that is dependent on something else, thus they do not use the subjunctive mood.