Explanation
In this vocabulary item, Declare is the closest synonym of Assert, so option B is correct. The word Assert and the word Declare 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 Assert with Declare keeps the core idea intact without reversing the tone or changing the action, quality or state expressed by the target word. The alternatives Keen, Unfriendly and Noticeable do not express the same central meaning as Assert. This distinction matters because competitive examinations often place one accurate synonym beside three familiar but contextually unsuitable words. To verify Assert independently, identify its part of speech, state a short definition, and place both Assert and Declare in the same simple sentence. If the sentence retains its essential meaning and grammatical structure, the synonym relationship is supported. Learners should revise Assert together with Declare, a brief usage cue and the contrasting distractors.