英语谜语和脑筋急转弯谜语what is yours,but is used by others than by your

英语谜语和脑筋急转弯
谜语
what is yours,but is used by others than by yourself?
I have cities without house,forest without trees.what am
what is always going but never gets anywhere?
脑筋急转弯
what is more usedful after it is broken?
what goes up and never gose down?
why is a river rich?
what word becomes 30 by taking off one letter