Words that are similar in meaning to each other are known as 'synonyms', and words that are quite unlike each other in terms of meaning are known as 'antonyms'. In this case, we have to find the word which IS a synonym of the word 'succinct', which refers to something that is concise, crisp and brief. Options A), B) and D) are unrelated to not just each other, but also the word 'succinct' itself - unusual refers to something that is not common; fleshy refers to something that is substantial and elaborate, and lastly narrow signifies something that is not wide in its scope. This leaves us with Option C) - Crisp, which is the correct answer.