In each of the questions given below, four words are

Solution

Let us examine the sentence carefully: Confidential communications → perfectly correct Deliberately manipulated → grammatically and contextually correct Public credibility → correct collocation Institutional scrutiny → highly appropriate phrase The entire sentence already conveys a coherent idea: → confidential communications were manipulated to protect institutional credibility during scrutiny. Now check possible swaps: A–B → “manipulated communications had been deliberately confidential” → grammatically illogical B–C → “public manipulated” → incorrect construction C–D → “institutional credibility” weakens contextual precision; “public scrutiny” changes intended meaning A–D → “confidential scrutiny” is meaningless in this context Thus, no interchange is required. Hence, option (D).