Limit of impurities
[化] 雜質極限; 雜質限度
?? 詞語組成解析
of
[?v]
prep. 關于;屬于…的;由…制成;
aux. 助動詞 [非標準用語、方言] =have [主用于虛擬語氣];
n. 雜質（impurity的復數）
??? 情景例句
Bon Voyage!
旅途愉快！
In college I majored in philosophy, What was your major?
大學時我主修哲學，你主修什么呢？
he always insisted that it should be written out in full.
但他還是堅持要求將信的全文寫在信紙上。