问题描述: on seeing me,he walked up to me,smiling这句话中seeing前面为什么要加on? 1个回答 分类:英语 2014-09-27 问题解答: 我来补答 on/upon后面接doing或sth 构成一个状语,表示“一……就……”On his arrival,he began to work 展开全文阅读