🧩 词语组成解析
radioactivity
[,redɪoæk'tɪvəti]
n. 放射（性）;辐射能;
radio光线+act行动，做+ivity表示情况、状态、“...性”、“...力” →放射性；[核] 放射能力；[核] 放射现象
unit
['ju:nit]
n. 单位，单元;装置;个体;[数]单位数;
🗣️ 情景例句
He looked up at me.
他仰头看我。
It's incredible.
令人难以置信。
The early climbers were looking for the easiest way to the top, because the summit was the prize they sought, especially if it and never been attained before.
早期登山者所寻找的是通往山顶的最方便的途径，因为顶峰特别是前人未曾到过的顶峰 -- 才是他们寻求的目标。