In each question, an incomplete statement (Stem) followed by fillers is given.…

Concept: "Despite" is a concession connector — it joins a clause describing an effort with a following clause stating an outcome contrary to what that effort aimed for. The completing clause must therefore describe a result that undermines the stated effort, not one that confirms its success.

Application: The stem states "his best efforts to conceal his anger." For "despite" to make grammatical and logical sense, what follows must show that the concealment did NOT work — his anger became apparent to others despite the effort to hide it. "People came to know that he was annoyed" states exactly this outcome: annoyance is the same emotion as anger, so others detected it even though he tried to hide it. This creates the required despite-contrast while keeping the emotion consistent between the two clauses.

Cross-check — why each other filler fails:

• "we could detect that he was very happy" swaps anger for an unrelated emotion (happiness), which has no logical connection to an effort at hiding anger.

• "he failed to give us an impression of his agony" says no impression came through at all — meaning the concealment worked, which agrees with the effort instead of contradicting it.

• "he succeeded in camouflaging his emotions" again affirms successful concealment, the opposite of the outcome "despite" requires.

• "he could succeed in doing it easily" is vague and never specifies whether the anger was detected or hidden, so it resolves nothing.

Answer: "people came to know that he was annoyed" is the only filler that completes the despite-contrast.