The correct answer is **穏やかな (odayaka na)**. This word means 'calm,' 'gentle,' or 'peaceful.' In the sentence 「（　　）、優しい人柄で、誰からも好かれている。」 (Because of their (calm), kind personality, they are liked by everyone.), **穏やかな** perfectly describes a person's temperament (**人柄 - hitogara**). It conveys the image of someone who is composed, not easily agitated, and mild-mannered, which aligns perfectly with 「優しい」(kind/gentle) and provides a clear reason for being well-liked. Common Mistakes / Nuances: ❌ : **派手な** means 'flashy,' 'showy,' or 'gaudy.' It is used to describe something that is very vibrant and attracts a lot of attention, such as clothing (**派手な服 - hade na fuku**) or makeup (**派手な化粧 - hade na keshou**). This is the opposite of a 'calm' and 'gentle' personality, making it unsuitable for the context. ❌ : **盛んな** means 'thriving,' 'prosperous,' 'popular,' or 'active.' It is typically used to describe activities, industries, or phenomena. For example, **スポーツが盛んだ (supootsu ga sakan da)** means 'sports are popular,' and **貿易が盛んだ (boueki ga sakan da)** means 'trade is thriving.' It does not describe a person's temperament or personality. Therefore, saying **盛んな人柄 (sakan na hitogara)** would be unnatural and incorrect. ❌ : **豊かな** means 'rich,' 'abundant,' or 'plentiful.' It can refer to material wealth (**豊かな生活 - yutaka na seikatsu**), nature (**豊かな自然 - yutaka na shizen**), or emotional depth and creativity (**感性が豊か - kansei ga yutaka**). While having a 'rich personality' (**豊かな人柄**) can be a positive trait, **豊か** does not carry the specific meaning of 'calm' or 'peaceful.' The word **穏やか** is much more precise for describing a gentle and tranquil disposition.

正解は**穏やかな（おだやかな）**です。この言葉は「落ち着いていて静かな様子」や「もの静かで優しい様子」を意味します。文の「（　　）、優しい人柄で、誰からも好かれている。」（（穏やかで）、優しい性格なので、みんなから好かれている）において、人の性格（**人柄 - ひとがら**）を説明するのに最適です。「穏やかな」は、落ち着きがあり、感情の起伏が激しくない、柔和な人物像を描写します。これは「優しい」という言葉とも非常によく合っており、「誰からも好かれている」理由として説得力があります。 Common Mistakes / Nuances: ❌ : **派手な** means 'flashy,' 'showy,' or 'gaudy.' It is used to describe something that is very vibrant and attracts a lot of attention, such as clothing (**派手な服 - hade na fuku**) or makeup (**派手な化粧 - hade na keshou**). This is the opposite of a 'calm' and 'gentle' personality, making it unsuitable for the context. ❌ : **盛んな** means 'thriving,' 'prosperous,' 'popular,' or 'active.' It is typically used to describe activities, industries, or phenomena. For example, **スポーツが盛んだ (supootsu ga sakan da)** means 'sports are popular,' and **貿易が盛んだ (boueki ga sakan da)** means 'trade is thriving.' It does not describe a person's temperament or personality. Therefore, saying **盛んな人柄 (sakan na hitogara)** would be unnatural and incorrect. ❌ : **豊かな** means 'rich,' 'abundant,' or 'plentiful.' It can refer to material wealth (**豊かな生活 - yutaka na seikatsu**), nature (**豊かな自然 - yutaka na shizen**), or emotional depth and creativity (**感性が豊か - kansei ga yutaka**). While having a 'rich personality' (**豊かな人柄**) can be a positive trait, **豊か** does not carry the specific meaning of 'calm' or 'peaceful.' The word **穏やか** is much more precise for describing a gentle and tranquil disposition.