on seeing me,he walked up to me,smiling这句话中seeing前面为什么要加on?

on seeing me,he walked up to me,smiling这句话中seeing前面为什么要加on? on seeing me,he walked up to me,smiling.求翻译 on doing用法有个句子 On seeing Mrs.Richards walk towards him,he fled.请问on doing 这个结构是怎么用的?什么情况下用? Much to my delight,( )seeing me,he walked up toMuch to my delight,( )seeing me,he walked up to me,smiling.A.atB.onC.forD.which 根据首字母提示补充句子.He stops to t_____ to me when seeing me.I need to s____ more time on practising football.Don't talk w____ your mouth full. ____the house on fire,he dialed 119.选seeing还是having seen答案是seeing ,但两者搞不清 walk me He e_____ seeing films 请问But he will not let me walk all over walk on He always walk to school on Monday morning. He always walk to school on Mondays morning.He always walk to school on Monday morning.He always walk to school on Mondays morning.哪个对、、急啊! 用英文翻译句子:He is too tired to walk on. he was so tired that he could not walk on中的walk on 很奇怪啊这啥用法啊 On seeing the plane coming towards me,I dashed for cover. 请翻译：On seeing the plane coming towards me,I dashed for cover. 17 He prefers_______there on rainy day(D)A to walking B walk C a walk D to walk选D是因为表目的吗?（page 17 no 4）18 Can you explain_____having done such a thing?(C)A me the reason for B the reason to me whyC the reason to me for D the reaso On seeing the plane coming towards me,I dashed for cover.是用了非谓语动词吗?On seeing是什么成分? He congratulated me on having won the competition.为什么介词要用on?还有这个：I dashed for cover on seeing the plan coming towards me.为什么也要用介词on来引导后面的动名词作宾语呢?这是属于那种用法,拜托高人