🧩 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
Have you been to our Tourist Information Center?
你去过我们的旅客服务中心吗？
Good morning, ladies and gentlemen. It's very satisfying to see so many of you here.
各位女士各位先生，早上好，在这里见到你们大家使人感到非常满意。
And anyone who gave more than a passing thought to the bottom confines of the oceans probably assumed that the sea bed was flat.
凡是稍稍想过大海海底的人大概都会认为海底是平坦的。