eg:She came across some old letters in the courseof her search.她在找東西時偶然發現了壹些舊信件。
run across sth./sbdy.與……不期而遇，偶然碰上（尤指令人愉快的人或事物）
eg:I ran across an old friend in the street.我在馬路上偶然碰見了壹個老朋友。