为什么是he puts up signs asking for help.那么to ask for

He also put up some signs asking for old bikes.为什么用asking不用t He also put up some signs asking for old bikes.为什么用asking ,用 Jim puts up some signs ___for old bikes.A to ask B asking 选哪 he put up some signs asking for bikes. He also put up some signs asking for old bikes.中的asking for He also put up some signs asking for old bikes and called up He also put up some signs asking for old bikes解释 [he put up some signs_(ask)someone for help] ·[he put up some signs_(ask)someone for help] he put up some signs____(ask)for help Asking For Help He kept ( )to his old friends to ask for help.