l'm looking for my glasses这句话的为什么不用look而要用looking呢?

every time i went back looking for sb为什么用looking而不是look~= = I`m looking for my purse 选择：I'm ( ) my book. A:looking at B:looking for C:looking Looking for my sou 请教looking for angel这句话的意思 looking forward to see you这句话为什么可以用looking 请解析一下以下着这句的look为什么要用looking? 英译汉I'm looking for a vest for my son. whom are you looking for 为什么是用 whom 为什么不用who I’m looking to this summer.look为什么加ing being brave doesn't mean you go looking for trouble 为什么look要 I'm stuck in a moment这句话为什么不用I而用I'm呢?