The correct answer is **異なる (ことなる)**, which means 'to differ' or 'to vary'. The sentence '人によって考え方が（異なる）のは当然だ' translates to 'It's natural that ways ofthinking differ from person to person.' This is the most suitable word because **異なる** neutrally describes a state where things are not the same, which perfectly fits the context of people having various ways of thinking. Common Mistakes / Nuances: ❌ : This word means 'to separate,' 'to leave,' or 'to be physically distant.' It's used for physical distance or parting. For example, '家族と離れて暮らす' (to live apart from one's family). While thoughts can be metaphorically 'far apart,' **離れる** is not used in this context to mean 'to differ.' It would sound unnatural. ❌ : This word means 'to oppose,' 'to be contrary to,' or 'to violate.' It implies that something goes against a specific rule, expectation, or principle. It's not used for a general state of difference. For instance, '法律に反する行為' (an act that violates the law). People's thoughts can differ without being in opposition to a specific standard. ❌ : This word means 'to go against,' 'to defy,' or 'to disobey.' It carries a strong nuance of active resistance against a force, authority, or trend. For example, '上司の命令に逆らう' (to disobey a superior's order) or '川の流れに逆らって泳ぐ' (to swim against the river's current). It describes an action of defiance, not a simple state of being different, making it inappropriate for this sentence.

正解は**異なる（ことなる）**です。「異なる」は「違う」「同じではない」という意味です。したがって、「人によって考え方が（異なる）のは当然だ」という文は、「人それぞれ考え方が違うのは当たり前のことだ」という意味になり、文法・意味ともに完全に成立します。**異なる**は、物事の状態が同じでないことを中立的に表現するのに最適な言葉です。 Common Mistakes / Nuances: ❌ : This word means 'to separate,' 'to leave,' or 'to be physically distant.' It's used for physical distance or parting. For example, '家族と離れて暮らす' (to live apart from one's family). While thoughts can be metaphorically 'far apart,' **離れる** is not used in this context to mean 'to differ.' It would sound unnatural. ❌ : This word means 'to oppose,' 'to be contrary to,' or 'to violate.' It implies that something goes against a specific rule, expectation, or principle. It's not used for a general state of difference. For instance, '法律に反する行為' (an act that violates the law). People's thoughts can differ without being in opposition to a specific standard. ❌ : This word means 'to go against,' 'to defy,' or 'to disobey.' It carries a strong nuance of active resistance against a force, authority, or trend. For example, '上司の命令に逆らう' (to disobey a superior's order) or '川の流れに逆らって泳ぐ' (to swim against the river's current). It describes an action of defiance, not a simple state of being different, making it inappropriate for this sentence.