all in vain

表示颜色的如"白菜"(chinese cabbage),"白熊"(polar bear),"白蚁"(termite_)表示徒劳的如"白费事"(all in vain),"白送"(give away,free of charge,for nothing)表示单纯的,不掺杂的如"白开水"(boiled water)"白肉"(plain boiled pork)在某种场...