_______entering the classroom,he found his students all talking and laughing loudly.A.On B.To C.For D.As答案：ＡＷＨＹ？

熱心網(wǎng)友

呵呵，樓上說的不錯(cuò)不過我覺得還可以有更確切的解釋ON可以加doing/由動詞轉(zhuǎn)換來的名詞，表示一……就……（固定用法）例如：He called her on his arrival。（arrival是由動詞arrive轉(zhuǎn)換而來的名詞哦）

熱心網(wǎng)友

由he found his students all talking and laughing loudly可知,是進(jìn)行時(shí),他剛進(jìn)教室的那一時(shí)刻同學(xué)門正在做此事,所以用ON表示進(jìn)來這一瞬間

熱心網(wǎng)友

on 是介詞,表示"一...就...",相當(dāng)于"as soon as ".B to 后跟動詞原形, C跟D意思不相符

熱心網(wǎng)友

翻譯：進(jìn)教室的時(shí)候，他發(fā)現(xiàn)········表示當(dāng)時(shí)發(fā)生的事情