All had betrayed him in his hour of need, but there he was, full of hope that the truth will prevail.
Use yet when introducing a contrast between two clauses, as it shows a shift in the situation or idea.
and there he was, full of hope
The sentence contrasts the betrayal of the subject with the display of hope. The word yet is the most fitting conjunction to show this contrast. - Option (A) still doesn't create a strong enough contrast between the betrayal and the hope. - Option (B) although does not fit well with the structure here and disrupts the flow of the sentence. - Option (C) yet effectively introduces a contrasting idea and fits the tone of the sentence. - Option (D) and simply connects the two parts but does not highlight the contrast adequately. Thus, Option (C) is the best choice.
Since the original sentence keeps the exact word order "there he was" after the connector, checking whether each option preserves this structure while supplying a suitable contrastive connector narrows down the choice quickly.
Only option C matches the original inverted word order and supplies a connector that correctly signals contrast.
Hence, the correct answer is Option C.