saw sb doing还是was doing

saw sb doing还是was doing sb was doing sth saw sb doing/do怎么用 excuse doing还是excuse sb doing mind sb do 还是doing persuade sb out of doing还是persuade sb from doing join sb in doing还是join sb doing keep sb doing还是keep sb do ? ? ? ? ? ? ? ? ? 我还是分不清楚see sb do sth see sb doing sthi saw him __on the bus while sb was/were doing与when sb was/were doing warn sb后跟to do 还是doing stand sb.doing还是to do?