The core concept is understanding translation. The most natural and accurate translation of 'He needs to take a deep breath' is '他需要深呼吸一次。', where '深呼吸' is the translation of 'a deep breath' and the verb 'take' in this context implies a single instance. Option B, 他需要深深地呼吸。, is grammatically correct but emphasizes ongoing deep breathing rather than a single instance. Option C, 他需要采取一个深深的呼吸。, is unnecessarily literal and sounds unnatural in Chinese. Option D, 他需要吸气。, only captures 'to inhale' and not the ‘deep breath’ component. The correct answer is A because it provides the most idiomatic and direct translation.