Unipolycondensation
單一縮聚作用
??? 情景例句
But personally I believe a business letter should end with Very truly yours, not Sincerely.
還行，喬治。但是我個人相信一封商業信函應該以“敬上”結尾，而不是“謹啟”。
Skiing is such a difficult sport that it's more work than play.
滑雪是非常困難的運動，真所謂工作高于游戲呀。
Then they had a second child-a son. How happy they were!
后來他們有了第2個孩子一個兒子。他們多么高興啊！