Tracer elements
[醫] 示蹤元素
?? 詞語組成解析
tracer
['treis?]
n. 追蹤者，描圖者，（鐵筆等）繪圖工具;
n. 原理, 基礎
??? 情景例句
His number is five, five, five, seven, five, three, two.
他的號碼是5557532。
In the world, who knows not to swim goes to the bottom.
處世似游泳，不會即下沉。
I don't know how to express my gratitude.
我不知道怎樣來表達我的感激之情。