Explanation
In this vocabulary item, Cure is the closest synonym of Heal, so option A is correct. The word Heal and the word Cure share the same central sense in the context tested by the question, although usage, tone and grammatical form should still be checked before substituting one for the other. A synonym is not required to be identical in every possible sentence; it must preserve the intended meaning in the relevant context. Here, replacing Heal with Cure keeps the core idea intact without reversing the tone or changing the action, quality or state expressed by the target word. The alternatives Doubtful, Nimble and Restrict do not express the same central meaning as Heal. This distinction matters because competitive examinations often place one accurate synonym beside three familiar but contextually unsuitable words. To verify Heal independently, identify its part of speech, state a short definition, and place both Heal and Cure in the same simple sentence. If the sentence retains its essential meaning and grammatical structure, the synonym relationship is supported. Learners should revise Heal together with Cure, a brief usage cue and the contrasting distractors.