Concept:An antonym is a word that means the opposite. "Perturbed" means feeling anxious, unsettled, or disturbed.Explanation:"Perturbed" describes a state of worry or unease. The opposite is a state of peace and composure. Among the options, "Unsettled", "Worried", and "Anxious" are all similar in meaning to "Perturbed" — they are synonyms, not opposites. Only "Calm" means free from nervousness or strong emotions, which is the direct opposite. For example, a calm person stays steady even in chaos. Thus, "Calm" is the correct antonym.Answer:Option D: Calm (शांत)