精巧

この機械は ___ な仕組みで動いている。

The correct answer is **精巧 (せいこう)**. "精巧な仕組み" describes a 'delicately' or 'intricately crafted' mechanism, emphasizing its complex and fine construction. This is a common and fitting collocation. **精密 (せいみつ)** means 'precise' or 'accurate,' often related to measurement or machinery that requires high accuracy. While a mechanism can be precise, "精巧" specifically highlights the intricate craftsmanship and delicate structural detail, making it a better fit for describing a *mechanism* that is elaborately made. **精算 (せいさん)** means 'exact calculation' or 'settlement of accounts.' It is a noun or verb and doesn't modify "仕組み" in this context. **精鋭 (せいえい)** means 'elite' or 'crack' (e.g., "精鋭部隊" - elite troops). It refers to the best of a group and doesn't apply to a mechanism.

正解は**精巧**です。「精巧な仕組み」は、非常に緻密で複雑な構成や作りを意味し、機械のメカニズムを表現するのに最適な言葉です。 「精密」は精度が高く正確であることを強調しますが、「精巧」はより複雑で巧妙な細工や構造に焦点を当てます。「精算」は計算を正確に行うことで、仕組みには使いません。「精鋭」は優秀な人材を指す言葉であり、仕組みには不適切です。