essential element的用法和樣例：
例句
- The theme is chosen in view of the human reliance on water as an essential element of life.
選擇此題材是由于水是人類(lèi)賴(lài)以為生的一個(gè)主要元素。 - Soon,the dance elements faded into the background and improvisation became the key element of the music.
但不久原本這些舞蹈的元素就隱退了，取代之而成為爵士樂(lè )主要元素的便是即興演奏。
